Thermoset volatile monomer molding compositions

ABSTRACT

A molding composition including reactive high-volatility monomeric groups, such as acrylics, at least one primary thermal initiator and at least one secondary thermal initiator is described. Molding processs using molding compositions including reactive high-volatility monomeric groups are also described.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a composition including volatile monomers,that is useful for thermoset molding and to methods for molding suchcompositions.

2. Description of the Related Art

Compositions for thermoset molding, also known as bulk molding compound(BMC), sheet molding compound (SMC) or thick molding compound (TMC), arewell known and widely used. The compositions can be formed into shapesby compression, transfer or injection molding. During the moldingprocess, thermally-initiated polymerization and/or crosslinkingreactions take place resulting in the compositions being polymerized or“cured” in the mold cavity shape. The resulting articles that exihibitheat resistance, strength, rigidity and dimensional precision. The typesof resins that are typically used include unsaturated polyesters,allyls, aminos, epoxies, phenolics and silicones. However, few of thesecompositions have been to be useful in producing articles/materials thathave the required aesthetics and fabricability for use in decorativesurfacing applications.

Acrylics, in general, have not been widely used for thermoset molding insolid surfacing applications because of the high volatility of theacrylic monomers, particularly methylmethacrylate. When introduced topreheated molds, a portion of the monomer can volatilize before thepolymerization/crosslinking reactions take place, resulting in poorerphysical properties and visual defects. Furthermore, conventionalmolding of such compounds often result in formation of internal andexternal voids, also related to the high volatility of the acrylicmonomers.

Acrylic molding materials including a single thermal initiator areknown. For example, published Japanese applications H9-110496A,H9-110497A, H9-111084A, H9-111085A, and H9-111086A disclose compositionsincluding methyl methacrylate monomer polymethyl methacrylate polymerand a resin polymer powder having a core-shell structure.

The molding of thermoset molding compounds is generally accomplished viathree fundamental molding techniques: compression molding, transfermolding, and injection molding. A description of these moldingtechniques can be found in Wright, Ralph E., Molded Thermosets; AHandbook for Plastics Engineers, Molders, and Designers, HanserPublishers, Oxford University Press, New York, 1991.

The choice of molding technique is largely determined by the design andfunctional requirements of the molded article and the need to producethe molded article economically. Although each of these methods bearsome resemblance to one another, each has its own design and operationalrequirements. Factors to consider in choosing a molding technique formaking an article include, for example, article design features, molddesign, molding procedures, press selection and operation, andpostmolding tools and fixtures.

Compression molding generally employs a vertical, hydraulically operatedpress which has two platens, one fixed and one moving. The mold halvesare fastened to the platens. The premeasured molding compound charge isplaced into the heated mold cavity, either manually or automatically.Automatic charging involves use of process controls and allows widerapplication of the molding process. The mold is then closed withapplication of the appropriate pressure and temperature. At the end ofthe molding cycle, the mold is opened hydraulically and the molded partis removed.

Compression molding mold design consists fundamentally of a cavity witha plunger. Depending upon final part design, the mold will have variousslides, ejection pins, and/or moving plates to aid in mold operation andextraction of the molded article. The mold flash gap and dimensionaltolerances can be adjusted to accommodate compound characteristics andpart requirements.

Transfer molding is similar to compression molding except for the methodin which the charge is introduced into the mold cavity. This techniqueis typically applied to multiple cavity molds. In this method, thecharge is manually or automatically introduced into a cylinder connectedto the mold cavities via a system of runners. A screw can be employed tointroduce the material into the transfer cylinder. A secondary hydraulicunit is used to power a plunger which forces the molding compoundthrough the runners and into the mold cavities of the closed mold. Avertical, hydraulic press then applies the needed pressure at theappropriate temperature to compression mold the intended part. Transfermold design is somewhat more complicated than that of compression moldsdue to the presence of the transfer cylinder and runners and due tointernal mold flow considerations, but general attributes are similar.Use of a shuttle press can be employed to allow encapsulation ofmolded-in inserts.

In general, injection molding is closely related to transfer moldingexcept that the hydraulic press is generally horizontally oriented, andthe molding compound is screw injected into the closed mold cavities viaa sprue bushing and a system of gates and runners. Pressure is thenapplied at the appropriate temperature to cure the part. The mold isopened for part ejection and removal, the mold is closed, and the nextcharge is injected by the screw. This thermoset molding technique has asignificant advantage in cycle time versus the other techniques listedabove. As such, it finds widespread use in multicavity moldingapplications. Injection mold designs are yet more complex and requirespecial attention to internal mold flow of the molding compound. In anextended application of injection molding, a vertically oriented shuttlepress can be employed to allow encapsulation of molded-in inserts.

In summary, the compression molding technique is primarily asemiautomatic method which typically exhibits the least part shrinkageand the highest part density, but has the longest cycle time, is limitedin ability to produce molded-in inserts, is limited in complexity ofmold design, and requires the most work to finish the molded product(flash removal). Transfer molding and injection molding aresemiautomatic and automatic methods, respectively, with shorter methodcycle times, excellent operability in producing molded-in inserts, andless work in finishing molded parts. Both techniquess typically exhibita lower part density and increased shrinkage versus compression molding.

Despite process differences in the molding techniques, thermoset moldshave several common features in their design and use. These molds areoften run isothermally; an optimal molding temperature is maintainedthroughout the molding cycle. For cycle time reasons, temperaturecycling of molds is not common in high productivity applications. Highproductivity molds are designed with internal channels for circulatinghot oil or with internal electric heating elements for faster moldheating response. If needed, cooling channels (oil or water) can beincluded. Molds can also be heated and cooled by contact withheated/cooled platens; this is representative of long cycle, low volumeproduction. Finally, typical thermoset molding cycles involve immediateapplication of the final molding pressure although pressure profiles(gradual application of pressure to a final selected molding pressurelater in cure cycle) are used in various situations.

SUMMARY OF THE INVENTION

This invention is directed to a molding composition which is suitablefor thermoset molding. The composition includes at least one volatilemonomer reactive material. The composition also comprises at least oneviscosity builder and at least two thermal initiators having differenttemperatures of activation. Unless otherwise stated, the weight percentvalue given is based upon the total weight of the molding composition.

Specifically, the composition comprises:

(a) from about 10 to about 25% by weight of a liquid polymerizablematerial including at least one volatile monomer reactive material;

(b) at least one viscosity builder;

(c) at least one primary thermal initiator having a primary thermalinitiator ten-hour half-life temperature; and

(d) at least one secondary thermal initiator having a secondary thermalinitiator ten-hour half-life temperature of at least about 5° C. greaterthan the primary thermal initiator ten-hour half-life temperature;

(e) optionally at least one non-crosslinked polymer;

(f) optionally at least one filler;

wherein at least about 0.05% by weight, is one or more crosslinkingagents.

The invention is further directed to methods for making an article fromthe molding composition described above. The method used generallydepends on the viscosity of the composition and the geometry of themold. The method also depends on the type of molded article to be made,i.e., a solid part or a part in which a non-reactive insert, or core, isencapsulated or coated.

In a first embodiment of the method, the composition is molded at asingle temperature and pressure. In general, the mold charge unit(s) isheated in a closed mold to a temperature sufficient to cause thesecondary thermal initiator to pass through about 3-10 half lives withinabout ten minutes or less, and held at a pressure sufficient to maintainthe internal and surface integrity of the mold charge, preferably fromabout 500-1500 psi (35-105 kg/cm²). This embodiment is particularlyuseful when one of two preferred conditions is met: (a) the mold has aflash gap tolerance not greater than about 130 microns; or (b) thereactive composition has a spiral flow length no greater than about 150cm, preferably no greater than about 100 cm.

In a second embodiment of the method, the composition is molded using adual temperature profile at a single pressure. In general, the moldcharge unit(s) is placed into a mold cavity of a mold having an initialmold temperature that is no greater than about 10° C. less than theboiling point of the most volatile component. Preferably, the mold ispreheated to reduce cycle time. More preferably, the mold is firstheated to an initial temperature that is at least about 50° C. The moldis then closed and a pressure is applied to a molding pressuresufficient to maintain the internal and surface integrity of the moldcharge, preferably about 500-1500 psi (35-10OS kg/cm²). The moldtemperature is then increased to a temperature sufficient to cause thesecondary thermal initiator to pass through about 3-10 half lives withinabout ten minutes or less. The mold is then cooled to the originaltemperature prior to removal of the molded article. For this embodimentalso, the method is particularly useful when one of two preferredconditions is met: (a) the mold has a flash gap tolerance not greaterthan about 130 microns; or (b) the reactive composition has a spiralflow length no greater than about 150 cm, preferably no greater thanabout 100 cm. In addition, this method is particularly useful forintricate mold patterns requiring multiple charges of moldingcomposition, for molded articles having at least one high-gloss surface,and also for encapsulating non-reactive core materials. Furthermore, itcan be useful for injection molding.

In a third embodiment of the method, the composition is molded at aconstant temperature and with a dual pressure profile. In general, thethermoset molding composition is placed in the mold cavity of a moldthat is preheated to a temperature sufficient to cause the secondarythermal initiator to pass through about 3-10 half lives, preferablywithin about ten minutes or less. An initial molding pressure sufficientto fill the mold with the mold charge, preferably of from about 100-500psi (21 to 35 kg/cm²) is applied and maintained for a time sufficient toseal the flash gap, preferably for about 30-90 seconds. The pressure isthen increased to a selected molding pressure sufficient to maintain theinternal and surface integrity of the mold charge, preferably about500-1500 psi (35-105 kg/cm²). The mold temperature and a final moldingpressure are maintained for a time sufficient for the secondary thermalinitiator to complete from about 3-10 half lives. In general, thismethod is useful for lower viscosity compositions where there is a needto flow in complex parts.

In a fourth embodiment of the method, the composition is molded with adual temperature profile and dual pressure profile. In general, themolding composition is first placed in the mold, which has an initialmold temperature of no greater than about 10° C. less than the boilingpoint of the most volatile component. The mold is preferably preheatedto reduce cycle time. More preferably, the mold is preheated to aninitial mold temperature of at least about 50° C. The pressure isapplied to fill the mold with the mold charge, preferably to about300-500 psi (21 to 35 kg/cm²) and maintained for a time sufficient toseal the flash gap, preferably for about 30-90 seconds. Preferably atthe same time the mold is closed (again, to reduce cycle time), the moldis heated to a temperature sufficient to cause the secondary thermalinitiator to cycle through from about three to about ten half liveswithin about ten minutes or less. The pressure is then increased to aselected molding pressure sufficient to maintain the internal andsurface integrity of the mold charge, preferably about 500-1500 psi(35-105 kg/cm²). The mold temperature and a final molding pressure aremaintained for a time sufficient for the secondary thermal initiator tocomplete from about 3-10 half lives. In addition, this method isparticularly useful for intricate mold patterns requiring multiplecharges of molding composition, for molded articles having at least onehigh-gloss surface, and also for encapsulating non-reactive corematerials. Furthermore, it can be useful for injection molding.

The invention is further directed to a molded articles made from thecomposition described above.

The invention itself, together with further objects and attendantadvantages, will best be understood by reference to the followingdetailed description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The Molding Composition

The compositions of the invention are useful for forming polymericarticles by thermoset molding processs. The term “article” is intendedto include both sheet materials and three-dimensional parts. The articlecan have a non-reactive core or insert encapsulated or coated by thethermoset molding composition. By “non-reactive” is meant that thematerial does not participate in the thermoset reactions during themolding process, although some interactions may take place at or withinthe surface of the non-reactive insert. (For example, some of thecomponents of the molding composition may permeate into the outersurface layer of the insert and react during the molding process so thata gradient adhesive layer with the outer insert layer is formed.) Thearticle can also have a layered structure in which the moldingcomposition is adjacent to one surface of a sheet or structure made froma different composition.

The molding composition of the present invention are at least 95% curedwhen heated in a closed mold at a temperature of about 100° to about145° C. for about 10 minutes or less. By “95% cure” it is meant thatless than 5% by weight of the monomer (based upon the weight of theliquid polymerizable material) remains unreacted.

Liquid polymerizable material

The liquid polymerizable material is a liquid starting material. By“liquid” is meant that the material is fluid at room temperature. TheBrookfield viscosity of the liquid can be as high as 20000 cps, asmeasured at 40° C. The liquid polymerizable material may include one ormore of the following: (a) at least one volatile monomer reactivematerial; (b) at least one nonvolatile monomer reactive material, and(c) at least one oligomeric reactive material. The present invention isparticularly useful where the liquid polymerizable material includes atleast one volatile monomer reactive material, and optionally, (a) atleast one nonvolatile monomer reactive material, and/or (b) at least onenonvolatile oligomeric reactive material.

It will be appreciated that the choice of liquid polymerizablematerial(s) will depend to some extent on the desired properties of thefinal molded article. For example, if adhesion to a hydrophilicsubstrate is desired, an acrylic material with acid or hydroxyl groupscan be used. For flexibility, (meth)acrylates with lower T_(g), such asbutyl acrylate, can be used. For thermal stability, it is preferred thatacrylates be used in combination with methacrylates. For enhancedhardness, it is preferred that high T_(g) (meth)acrylate functionaloligomerbe used.

(a) Volatile monomer reactive material

By “volatile monomer reactive material,” it is meant a low-boiling pointmonomeric material including at least one site of unsaturation that isco-polymerizable in a radical-initiated addition polymerizationreaction. In general, useful volatile monomer reactive materials haveboiling points of less than the highest molding temperature, measured atatmospheric pressure (1 atm). The present invention is especially usefulfor molding compositions including at least one volatile monomerreactive material having a boiling point of less than about 110° C.Suitable volatile monomer reactive materials can include, for example,monomers having at least one acrylic group, monomers having at least onevinyl group, monomers having both acrylic and vinyl groups, substitutedbutadienes or combinations thereof.

Examples of volatile monomer reactive materials including at least oneacrylic group includes methyl (meth)acrylate and ethyl (meth) acrylate,where the term “(meth)acrylate” refers to acrylate, methacrylate andcombinations thereof. Examples of volatile monomer reactive materialsincluding at least one “vinyl group” includes acrylonitrile,methacrylonitrile, and vinyl acetate.

Other useful liquid polymerizable materials include those thatpolymerize under the same conditions as the volatile monomer reactivematerials. In one embodiment, these other liquid polymerizable materialis preferably fully miscible with the volatile monomer reactivematerial. Examples of suitable liquid polymerizable materials includeacrylics, allyls and other vinyl monomers, siloxanes, and silanes.Combinations of liquid polymerizable materials can also be used.

(b) Nonvolatile monomer reactive material

Nonvolatile monomer reactive materials can generally be used to adjustphysical and/or the aesthestic properties of the molded article. Onetype of suitable non-volatile monomer reactive material is an ester ofacrylic or methacrylic acid. The ester is generally derived from analcohol having 3-20 carbon atoms. The alcohols can be aliphatic,cycloaliphatic or aromatic. The ester may also be substituted withgroups including, but not limited to, hydroxyl, halogen, and nitro.Representative (meth)acrylate esters include butyl (meth)acrylate,2-ethylhexyl (meth)acrylate, glycidyl (meth)acrylate,cyclohexo(meth)acrylate, isobornyl(meth)acrylate, siloxane(meth)acrylate, and the like. Acrylic and methacrylic acid can also beused. Other types of reactive acrylic materials include acrylicfunctionalized materials such as, for example, urethane (meth)acrylatesformed by (meth)acrylic functionalization of urethane oligomers or by insitu reaction of oligomeric isocyanates with (meth)acrylic residues;epoxy (meth)acrylates, such as the mono- and di(meth)acrylates ofbisphenol A epoxy resins; (meth)acrylate functionalized unsaturatedpolyester oligomers and resins. By “acrylic functionalized material” itis meant any compound that has at least one reactive (meth)acrlic groupappended on the material. Combinations of reactive acrylic materials canalso be used.

(c) Oligomeric reactive material

An oligomeric material is “reactive” when the material physicallyassociates or chemically reacts with any other component(s) in themolding composition. Oligomeric reactive materials can include oligomersof any of the (a) and/or (b) monomers described above, urethanes,unsaturated polyesters, epoxies and combinations thereof. Preferably,the oligomeric reactive material is incorporated into the polymerizedmaterial making up the molded article during the molding process.

In thermoset molding, the final molded article is frequently smallerthan the mold cavity due to volume contraction during the polymerizationprocess. The difference between the mold dimension and the dimension ofthe final molded article, usually measured along the longest edge, isreferred to as shrinkage. In the molding industry, it is desirable tominimize and characterize shrinkage in order to facilitate mold designand accurately predict and reproduce part dimensions.

To minimize overall shrinkage in the formation of the molded article, itis preferred that the amount of volatile monomer reactive material andnonvolatile monomer reactive material, when used, is no greater thanabout 25% by weight, preferably no greater than about 18% by weight,based on the total weight of the molding composition. Preferably, aminimum amount of (nonvolatile and/or volatile) monomer reactivematerial(s) is present to provide sufficient liquid viscosity tofacilitate processability. More preferably, this minimum amount is about5% by weight, most preferably about 10% by weight, based on the totalweight of the molding composition. Oligomeric reactive materials arealso used to replace the polymerizable monomer (i.e., the nonvolatilemonomer reactive material and the volatile monomer reactive material) asa means to reduce overall shrinkage of the molded article.

The present invention is particularly useful for a molding compositionwherein at least about 1% by weight of the liquid polymerizable materialis a volatile monomer reactive material; more particularly useful whereat least about 20% by weight of the liquid polymerizable material is avolatile monomer reactive material; most particularly useful where atleast 50% by weight of the liquid polymerizable material is a volatilemonomer reactive material.

The total amount of liquid polymerizable material in the moldingcomposition is generally present in an amount of from about 10 to about25% by weight, based on the total weight of the molding composition.Preferably, the liquid polymerizable material is from about 10 to about20% by weight of the total molding composition.

Non-crosslinked Resin Polymer

The molding composition of the present invention optionally includes atleast one non-crosslinked resin polymer. Non-crosslinked resin polymersof the present invention can be reactive, nonreactive or a combinationthereof. A non-crosslinked resin polymer is “reactive” when the polymerphysically associates or chemically reacts with any other component(s)in the molding composition.

In a preferred embodiment, the reactive non-crosslinked resin polymersare also incorporated into the polymerized material making up the moldedarticle during the molding process. The term “non-crosslinked” as usedherein refers to polymers that are linear, branched, blocked orcombinations thereof, that, as a starting material prior to introductionto the molding composition have chains without linkages between thechains. The non-crosslinked resin polymer contributes to the strengthand other physical properties of the molded article, and lowers theamount of liquid polymerizable material needed.

The non-crosslinked polymer can either be soluble or insoluble in theliquid polymerizable material. The combination of the solublenon-crosslinked polymer dissolved in the liquid polymerizable materialis generally referred to as a “sirup”. Suitable polymers include, arebut not limited to, homopolymers and copolymers made from any of themonomers or oligomers listed above as liquid polymerizable material. Itis understood that any polymeric material can be used in the presentinvention as a non-crosslinked resin polymer, limited only by thedesired property of the final molded article.s.

Preferably, the polymer has a weight average molecular weight in therange of about 30,000 to about 200,000, more preferably from about60,000 to about 200,000. In one embodiment, the polymer can be added inthe form of beads having a median (d50) particle size in the range offrom about 100 to about 300 microns and mixed to dissolve. Beads havingsmaller particle sizes can also be used. Preferred non-crosslinkedpolymers are the homopolymers and copolymers of (meth)acrylate esters.

The non-crosslinked polymer(s), when present, is generally present in anamount of from about 1 to about 20% by weight, based on the total weightof the molding composition; preferably about 2 to about 10% by weight.

Fillers

The molding composition of the present invention optionally includes atleast one filler. Suitable types of fillers useful in the presentmolding composition include, for example, mineral fillers, decorativefillers, and functional fillers.

The mineral filler increases the strength of the final molded article.It will be understood, that in addition to strength, the mineral fillercan provide other attributes to the molded article. For example, it canprovide other functional properties, such as flame retardance, or it mayserve a decorative purpose and =* modify the aesthetics. Any mineralfillers known in the field of acrylic solid surfaces can be used in thepresent molding composition. Some representative mineral fillers includealumina, alumina trihydrate (ATH), alumina monohydrate, Bayer hydrate,silica including sand or glass, glass spheres, magnesium hydroxide,calcium sulfate, calcium carbonate, barium sulfate, and ceramicparticles. Combinations of mineral fillers can also be used.Furthermore, these mineral fillers can be optionally coat-treated withcoupling agents such as silane (meth)acrylate such as SilaneMethacrylate A-174 available from OSI Specialties (Friendly, W. Va.) orZelec® MO available from E.I. du Pont de nemours and Company(Wilmington, Del.). The mineral filler is generally present in the formof small particles, with an average particle size in the range of fromabout 5-200 microns.

The nature of the mineral filler particles, in particular, therefractive index, has a pronounced effect on the aesthetics of the finalmolded article. When the refractive index of the filler is closelymatched to that of the liquid polymerizable material afterpolymerization, the resulting molded article has a translucentappearance. As the refractive index deviates from that of the polymermatrix after polymerization, the resulting appearance is more opaque.The index of refraction of ATH is very close to that of polymethylmethacrylate (PMMA), and frequently ATH is a preferred filler forPMMA systems. For other polymer/filler systems, the refractive indicescan be adjusted to provide the desired appearance.

The mineral filler, when present, is generally present in an amount offrom about 10 to about 75% by weight, based on the total weight of themolding composition; preferably about 40 to about 70% by weight.

The molding composition can optionally include decorative fillers. Suchfillers, although they may have a minor effect on physical properties,are present primarily for aesthetic reasons. Examples of suitabledecorative fillers include largerparticles of unfilled and filledcrosslinked or uncrosslinked polymeric material. Such materialsgenerally have a particle size of from about 325 to about 2 mesh(0.04-10.3 mm in greatest average dimension) and can be, for example,pigmented PMMA particles filled with ATH. Alternatively, very largeparticle size fillers can be used. The decorative filler particle sizescan be greater than the mold cavity in the Z-dimension so that they canbe crushed upon application of ** pressure to give an interestingfractured aesthetic. Furthermore, decorative filler pieces significantlylarge in the X, Y-plane of the mold cavity (e.g., 1 to 6 inches) can beencapsulated but leaving one side exposed to give an interestingaesthetic. As the particle size and amount of the large polymericparticle filler is increased, it is generally necessary to adjust theamount of viscosity builder present to maintain consistent viscosity ofthe molding composition. Other types of decorative fillers include:pigments and dyes; reflective flakes; metal particles; rocks; coloredglass; colored sand of various sizes; wood products such as fibers,pellets and powders; and others. The decorative filler can be present inan amount of from 0 to about 80% by weight, based on the total weight ofthe molding composition; more typically, about 1 to about 25% by weight.

The molding composition can optionally include functional fillers. Suchfillers impart additional special properties for specific applications.Examples of such functional fillers include flame retardants,antibacterial agents, and others known in the art. The functionalfillers, when used, are present in an amount sufficient to be effective,but generally no greater than about 25% by weight. based on the totalweight of the molding composition.

The total amount of fillers present in a molding composition isgenerally from about 1-80% by weight, and preferably from about 40-70%by weight, based upon the total weight of the composition.

Viscosity Builders

The molding composition of the invention includes at least one viscositybuilder. The functions of the viscosity builder include to quickly andirreversibly reach a preferably stable viscosity of the moldingcomposition during the mixing process and to stabilize and maintain theviscosity of the molding composition during the mixing process in a waythat does not interfere with the polymerization reaction during themolding process. The viscosity builder further maintains the viscosityof the molding composition until the molding composition is used in themolding process.

Viscosity builders useful in the present invention increases viscosityof the molding composition through physical and/or chemical interactionswith other components in the molding composition. Viscosity buildersuseful in the present invention include (1) ionic crosslinkers, (2)chemical crosslinkers, (3)setting agents, (4) thickeners, andcombinations thereof. Of course, the suitable viscosity builder isfunctional at the mixing temperature for the molding composition (whichtemperature is preferably about 10-60° C., more preferably about 20-40°C.).

Preferably, the total amount of viscosity builder ranges between about0.1% and about 25% by weight.

(1) Ionic Crosslinkers

Ionic crosslinkers generally facilitate ionic interaction of a metal ionwith, for example, acid or hydroxyl residues. Examples of useful ioniccrosslinkers include magnesium hydroxide (MgOH) and various zinc salts.

(2) Chemical Crosslinkers

Chemical crosslinkers generally facilitate chemical condensationreactions such as, for example, condensation of polyisocyanates withhydroxyl residues.

(3) Setting Agents

Setting agents generally facilitate physical imbibition of liquidcomponents into solid materials. The setting agent useful in the presentinvention can be (a) an organic polymeric fiber, (b) a fine particulatepolymeric material, (c) a polymer/filler composite, or combinationsthereof. Suitable setting agents are compatible with the liquidpolymerizable material and results in rapid increased viscosity in themolding composition upon mixing. By “rapid increased viscosity”, it ismeant that the viscosity of the molding composition increases withinabout 5 hours or less, preferably within about 1 hour or less. In apreferred embodiment, the compatible setting agent meets one of twoconditions: (1) the setting agent does not form a separate phase in themolding composition; (2) if the setting agent does form a separatephase, and has a refractive index sufficiently close to that of theliquid polymerizable material after polymerization so that the separatephase is not visible in the molded article. In general, the settingagent is a high Tg polymeric material which absorbs or imbibes thecomponents of the liquid polymerizable material.

Suitable monomer-absorbing organic polymeric fibers (a) include, forexample, polyester fibers that provide improved process latitude byabsorbing polymerizable monomer and subsequently sealing the flash gapof the mold quickly.

Fine particle polymeric materials are generally prepared directly byeither suspension or emulsion polymerization. Suspension polymerizationis a generally practiced technique which generally affords polymer beadshaving a particle size in the range of 80-130 microns. The particles aremade of many polymer chains with weight average molecular weightsgenerally no greater than 100,000. The polymer particles are solid andnon-porous. Emulsion polymerization is a well-known practiced techniquewhich typically affords a water-borne dispersion of particles, generallyreferred to as primary particles, between 0.2 and 2 microns in diameter.The particles generally are made of only one polymer chain with weightaverage molecular weights in excess of 500,000 and generally greaterthan one million. The polymer particles can be porous, depending uponthe drying technique.

Polymeric materials suitable as setting agents (b) are generally made byemulsion polymerization. Aqueous dispersions of polymers prepared byemulsion polymerization, typically referred to as latices, can be driedusing a variety of techniques, such as freeze-drying, drum drying andspray drying. Each technique has its own requirements regardingtemperature of operation and rate of water removal. As the water isremoved, the polymer particles tend to agglomerate. As this isaccompanied by increasing amounts of heat, the polymer particles willtend to coalesce, losing their individual identity and forming a largerparticle with reduced surface area. Furthermore, if the drying methoddoes not employ severe temperatures, the level of coalescence can beminimized to greatly increase the available surface area morphology ofthe polymer particle. The resulting high surface area, porous polymerparticle with a size ranging from 2-150 microns offers an ability toimbibe free monomer quickly to rapidly build viscosity to a stable andreproducible level.

Dried latex particles with a median (d50) particle size of from about 30to about 150 microns have been found to be the most effective.Furthermore, it is also preferred that the agglomerate particles havemorphologies that are friable, thus readily separating into smallerparticles and thereby providing greater surface area for rapid liquidimbibition.

Emulsion polymerization is a well-known technique and has been describedin, for example, Sanderson, U.S. Pat. No. 3,032,521, Hochberg, U.S. Pat.No. 3,895,082, and Fryd et al., U.S. Pat. No. 4,980,410. The emulsionpolymerization process can be controlled to produce polymeric particleshaving a molecular weight (weight average) in excess of one million. Ingeneral, polymeric particles having weight average molecular weights inthe range of about 500,000 to about 2,000,000 are useful in thecompositions of the invention. For the compositions of the invention,the polymeric setting agent should have a Tg greater than 50° C.;preferably greater than 80° C.; most preferably greater than 90° C.

Examples of suitable polymers that can be used as a setting agentinclude homopolymers and copolymers of: acrylic acid; methacrylic acid;(meth)acrylate esters of alcohols having 1-20 carbon atoms; vinylethers; vinyl esters; acrylonitrile; methacrylonitrile; acrylamide;methacrylamide; styrene, including substituted styrenes; butadiene.Combinations of polymers can also be used. A preferred type of settingagent is a (meth)acrylic polymer or copolymer.

The setting agent particles can also have core-shell structure in whichthe monomers polymerized to form the core of the particle differ fromthose polymerized to form the shell. Such core-shell particles have beendescribed in, for example, Fryd et al., U.S. Pat. No. 4,726,877. Theshell can be crosslinkable, functioning as an additional crosslinkingagent in the molding composition.

Polymer particle setting agents suitable for the compositions of theinvention, are available commercially as PARALOID(R) K-1120N-D, 99-100%poly(methylmethacrylate/ethylacrylate from Rohm and Haas (Philadelphia,Pa.); Kane Ace FM-25, 98% poly(methylmethacrylate/acrylic) core-shellcopolymer from Kaneka Texas Corp. (Pasadena, Tex.); Elvacite(R) 2896 andElvacite(R) 2041, both 99% polymethylmethacrylate from ICI Acrylics,Inc. (Wilmington, Del.).

Another type of setting agent is a polymer/filler composite (c). Onesuch composite setting agent is prepared by spray drying an aqueouslatex dispersion with a mineral filler such as ATH. The resulting drypowder is comprised of a filler particle with a thin coating ofcoalesced latex. This structure affords a high surface area polymer. Italso offers an advantage in that the setting agent polymer ispredispersed in the mixture by its association with the filler surface,which aids in method design and helps to avoid material inhomogeneitiesin the molding compound resulting from incomplete mixing and wetting ofthe polymer particle setting agent. Such composite materials have beendescribed in, for example, Sasaki et al., U.S. Pat. No. 4,678,819.

A second composite setting agent is derived from the dust generatedduring the milling, sawing, and sanding of filled polymer decorativesolid surface materials. Such dust generally has particles withparticlesizes in the range of from about 5 to about 250 microns. Amedian particle size of about 60 microns has been found useful.

Preferably, the molding composition includes from about 2% to about 20 %by weight of setting agents.

(4) Thickners

Thickeners generally facilitate an increase in viscosity through thebuilding of structure between thickener and filler particles. Examplesof suitable thickeners include silicas and structured silicas andzeolites.

Primary Thermal Initiator

The primary thermal initiator (primary initiator), when heated,generates free radicals which initiate the polymerization reactions. Thegeneral function of the primary thermal initiator is to facilitate thepolymerization reaction in the molding composition during the initialperiod, preferably the first minute, of the reaction. Factors that maybe used in choosing the type of initial and secondary thermal initiatorsinclude the intended cycle time, mold temperature and the ceilingtemperature of the volatile reactive monomer(s). By “ceilingtemperature” it is meant the temperature at which the polymerization anddepolymerization of the monomer(s) reaches equilibrium. In addition, ingeneral, the lower the half-life temperature of the thermal initiator,the shorter the shelf life of the molding composition. Thus, it ispreferred that the primary thermal initiator have a ten-hour half-lifetemperature in the range of from about 40 to about 80° C. The “ten-hourhalf-life temperature” is a conventional measure of initiators whichindicates the temperature at which one-half of the initiator willundergo decomposition to provide initiating radicals within ten hours.The thermal initiators are generally either peroxy compounds or azocompounds. Illustrative compounds include t-butylperoxyneodecanoatewhich has a ten-hour half-life temperature of about 48° C., availablecommercially as Lupersol® 10M75 from Elf Atochem, King of Prussia, Pa.);and t-butylperoxypivalate which has a ten-hour half-life temperature offrom about 58° C., (available commercially as Lupersol® 11 from ElfAtochem). An azo initiator is commercially available as Vazo® 52 from E.I. du Pont de Nemours and Company (Wilmington, Del.) which has ten-houra half life temperature of 52° C. The primary thermal initiator isgenerally present in an amount of from about 0.01 to about 5%,preferably from about 0.02 to about 1.0% by weight, based on the totalweight of the molding composition.

Secondary Thermal Initiator

The general function of the secondary thermal initiator (secondaryinitiator) is to complete the polymerization reaction(s) after theprimary thermal initiator is essentially depleted. The ten-hourhalf-life temperature of the secondary thermal initiator is preferablyat least about 5° C., more preferably about 8-20° C. greater than theten-hour half-life temperature of the primary thermal initiator.Preferably, the ten-hour half-life of the secondary initiator is in therange of from about 60 to about 120° C., more preferably about 60-80° C.In most cases, the secondary thermal initiator is an azo compound. Anillustrative compound is 2,2-azobis(methylbutyronitrile) which as aten-hour half-life temperature of from about 67° C., commerciallyavailable as Vazo® 67 from E. I. du Pont de Nemours and Company(Wilmington, Del.). The secondary thermal initiator is generally presentin an amount of from about 0.001 to about 1%, preferably from about0.005 to about 0.5% by weight, based on the total weight of the moldingcomposition.

The amount of primary and secondary thermal initiators used in themolding composition are often dependent upon the desired cycle time andcompleteness of polymerization in the molding process. In addition, thetypical mole ratio of primary thermal initiator to the secondary thermalinitiator ranges from about 3 to about 6, preferably from about 5 toabout 6.

Crosslinking Agents

The composition of the invention includes an effective amount,preferably at least about 0.05% by weight, based on the total weight ofthe composition, of at least one crosslinking agent. The crosslinkingagent is generally a multifunctional material having more than onereactive group that reacts with the liquid polymerizable material andother reactive materials (such as the reactive non-crosslinked resinpolymer) at the molding temperature. The reactive group can be one whichcopolymerizes with the liquid polymerizable material, such as apolymerizable ethylenically unsaturated group. The reactive group canalso be one which reacts with a side chain or residue of the liquidpolymerizable material after polymerization, such as a hydroxyl,carboxyl, isocyanate or epoxy group. The reaction of the multifunctionalreactive material forms a crosslinked network with the liquidpolymerizable material.

Crosslinking resins can be used as crosslinking agents, such as epoxies,novolacs, amino resins, and (meth)acrylated resins.

The crosslinking agent can be a liquid polymerizable material, generallya multifunctional monomer or oligomer. A preferred class of crosslinkingagents is the (meth)acrylate esters of polyols. Some representativeexamples include ethylene glycol di(meth)acrylate, hexanedioldi(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritoltri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, and the like.Other suitable types of crosslinking agents include divinyl compounds,such as divinyl ethers, allyl (meth)acrylate, urethane di- andpoly-(meth)acrylates.

The crosslinking agent can be a non-crosslinked polymer having multiplereactive groups. The reactive groups can be pendant to or in the mainchain of the polymer.

The crosslinking agent can be a setting agent having multiple reactivegroups. The reactive groups can be present throughout the setting agentpolymer, or they can be present only at the surface of the setting agentparticle, for example, in the shell polymer(s) of a core-shell microgelsetting agent.

It is understood that the crosslinking agent can also be any combinationof the above-described liquid polymerizable material, non-crosslinkedpolymer and setting agent or a material outside of these describedmaterial groups. It is further understood that a component useful in thepresent invention that functions as a crosslinking agent at the moldingtemperature can also function as a viscosity builder at the mixingtemperature when the component has reactive groups with differentreactivities (e.g., one group reacting at the mixing temperature, whilea separate group reacting at the molding temperature). For example, (1)a useful component may contain two isocyanate reactive groups whereinone isocyanate group is blocked at the mixing temperature and becomesunblocked at the molding temperature; (2) a useful component may containisocyanate and epoxy reactive groups; and (3) a useful component maycontain isocyanate and acrylic reactive groups.

The amount of crosslinking agent present often affects the physicalproperties and the polymerization cure time of the molded article.Increased levels of crosslinking agent improve the hot strength of thearticle, i.e., the structural integrity of the article when removed fromthe mold while still hot. With lower levels of crosslinking agent, themolded article should be cooled before removing it from the mold becauseit is still too flexible and flowable when hot. Generally, increasingthe level of crosslinking agent also increases the brittleness of themolded article and can lower the impact strength and toughness. Thefinal level of crosslinking agent is determined by balancing these andother desired properties. The nature of the crosslinking agent can havea significant impact on the physical properties of the molded article.Combinations of crosslinking agent material can be optimized to offerdesired hot strength without severely impacting physical properties. Theamount of crosslinking agent depends upon the equivalent weight of thecrosslinking agent and the intended use of the molded article. By“equivalent weight” it is meant the molecular weight of the crosslinkingagent divided by the number of reactive groups on the crosslinkingagent. In general, the crosslinking agent is present in an amount of atleast about 0.05% by weight, based on the total weight of the moldingcomposition, preferably at least about 0.2% by weight; more preferablyat least about 1% by weight.

Other Ingredients

The molding composition can optionally include fiber reinforcement foradditional impact, flexural and tensile strength. Useful forms of fiberinclude, free fibers, woven or nonwoven mats, cloth or veils andcombinations thereof. The fibers can be polyester, polyaramid, sized orunsized glass, carbon fibers, or liquid crystal fibers. Monomerabsorbing fibers, such as those useful as setting agents, are generallynot visible in the molded article. Polyaramid and carbon fibers providetoughness as well as method latitude, but generally are visible. Glassfibers provide method latitude and aesthetics, but can also causestaining. The fibers can be prewet with liquid polymerizable materialprior to adding to the composition. The nonwoven or woven fiber mats canalso be embedded as a surface treatment on one or both sides of themolded article. Alternatively, the fiber mat can be encapsulated in themolded article. The fibers are generally present in an amount of up toabout 50% by weight, based on the total weight of the moldingcomposition. In one embodiment, the fibers are present in an amount ofabout 5-10% by weight.

The molding compositions can also contain coupling agents. Couplingagents generally have dual functionality: one end having a polymerizablegroup which can copolymerize with the liquid polymerizable material; theother end having a group which complexes with or has an affinity for theparticulate mineral filler(s). Thus, coupling agents can be used as anaid in wetting the particulate filler with the liquid polymerizablematerial. For (meth)acrylate/ATH systems coupling agents which areparticularly useful are those having (meth)acrylate functionality and aphosphate or silane group. These coupling agents can be added as apre-treatment to mineral fillers during the production method, asreferred to in the previous section describing fillers. Alternatively oradditionally, these coupling agents can be added in situ to the moldingcomposition. Examples of commercially available coupling agents includeZelec® MO from E. I. du Pont de Nemours and Company (Wilmington, Del.)and as A-174 from Osi Specialties, a subsidiary of Witco (Friendly, W.Va.). In general, up to about 0.5% by weight of the total moldingcomposition can be coupling agents.

Other additives which can be present in the molding composition includeinternal mold release agents such as zinc stearate, the sodium salt ofdioctyl sulfosuccinate (such as Aerosol™ OT-S Surfactant (70% solutionsodium salt of dioctyl sulfosuccinate in petroleum naphtha) availablefrom Cytec Industries Incoporated, West Patterson, N.J.), zinc octoate,and silicone oils and (meth)acrylate functionalized silicones andsiloxanes; wetting agents; surfactants; antioxidants; plasticizers andother components known to be used in polymeric materials.

For thermoset molding, the compositions should have a consistencysimilar to bread dough, or even thicker. It is difficult to measureviscosity reliably for materials this thick. A better measure of this isthe spiral flow length. The spiral flow length given herein are valuesdetermined by the spiral flow length measurement technique described inthe Examples.

For thermoset molding, the composition preferably has a spiral flowlength of less than about 40 inches (102 cm) for an isobaric process. Aspiral flow length of greater than about 40 inches (102 cm)is preferredfor a process involving a pressure profile. Of course, the higher theviscosity, the shorter the spiral flow length.

Molding Composition Preparation

The molding compositions can be prepared, in general, simply by mixingthe components at high shear. This is generally accomplished in a deviceknown as a kneader. For batch methods a kneader/extruder, a twice-screwextruder or the like can be used. For continuous methods, a Buss or Listkneader can be used. Such mixers are well known in the food industry andcompounding industry.

In general, the components are mixed in order in one of two sequences.In one sequence, all the liquid components are first mixed together. Tothis is added the mineral filler(s) (if present), the setting agent(s)(if present), and the thickener(s) (if present), which can all bepremixed. Finally, all the other components can be added. In a secondsequence, the mineral filler and the setting agent are first mixedtogether. To this is added the liquid components individually. Finally,all the other components are added. The choice of mixing sequence isdependent upon the nature of the process requirements.

It is understood that other mixing orders can be used to prepare themolding composition. It is further understood that the mixingtemperature should be maintained to prevent the onset of polymerization.Preferably, the mixing temperature is maintained between about 10-60°C., more preferably, between about 20-40° C.

The composition, as formed, is suitable for molding immediately, eventhough the viscosity may continue to increase slightly over time (e.g.,about 24 hours).

Post-Mixing Compound Treatments Packaging, and Storage

Once the molding compound is prepared by the suitable mixing orcompounding method, it can be packaged and delivered either in bulk formor as a preshaped charge, Preshaping is generally done either bycompressing a measured amount of the molding compound in an unheatedmold designed to provide a charge in the proper shape or byconsolidating and extruding the molding compound through a specificprofiling die and cutting the profile into measured lengths consistentwith the needed charge weight or injection feeder design. The latter canbe continuously fed from a continuous mixer, if needed. The moldingcompound (bulk form or preshaped charge) is then packaged in animpermeable plastic bag. The sealed bags are then packaged in rigidcontainers and stored or shipped, preferably under refrigeration.

In an extension of the extruded profiling method above, the moldingcompound can be continuously extruded through a slit die, in between twopolymer film sheets and into a calendering system to produce acontinuous SMC profile. The compound is rolled up and sealed for storageor shipping.

Molding compound may be stored at refrigerated temperatures until use inorder to preserve the activity of the thermal initiators which are partof the thermoset formulation; utility of this action is dependent uponthe nature of the thermal initiators involved. Typical storagetemperatures range from 5° C. to ambient temperature. Shelf life ofcommercial molding compounds range up to 6 months, dependent uponstorage condition practices.

In a production molding environment, the compound will be either used asdelivered or fed into a mechanical preformer which shapes the materialinto a specific shape of known density for use in the intended moldingapplication. Preforming can also be carried out in a continuous fashionas outlined above. The preshaped charge then may or may not be preheatedto a temperature below that needed to effect polymerization, but at ahigh enough temperature to aid in compound flow inside of the mold. Itis preferred to carry out preforming of the molding compositionimmediately after mixing. This is especially true for forming an SMCformat.

Molding Process

The molding composition of the present invention can be used in all ofthe conventional molding techniques: compression molding, transfermolding, and injection molding.

The temperature and pressure conditions in the molding process of thepresent invention are dependent on a number of factors. One factor isthe rheology of the molding composition. Different thicknesses orviscosities may require different temperature and/or pressure profilesas a function of their cure packages. A second factor is the moldingtechnique chosen. The geometry of the mold is also a factor. Onecritical feature of the mold is the so-called “flash gap” or “flashtolerance”. This term indicates any open space between mold halvesand/or mold components after the mold is closed through which theuncured molding composition can be forced by pressure. The flash gap(s)should be filled by molding composition and the compositions partiallycured before the mold is completely sealed for application of finalmolding pressure. The shape of the mold is another consideration. Moreintricate designs for finished articles, such as, for example, molded-inholes, differential thicknesses, screw inserts, multiple draft angles,or moving components may require multiple charges of moldingcomposition, and good internal mold flow prior to polymerization. Thiswill affect the pressure and temperature profiles. The moldingconditions are also dependent on the type of molded article to be made,i.e., a simple solid part, or a part in which a non-reactive core isencapsulated.

As used herein, the term “mold charge” refers to an amount of moldingcomposition to be molded into a molded article. It is understood that,depending upon features of the final molded article and/or the geometryof the mold cavity, the charge can be a single unit or a multiple unitcharge (i.e., the mold charge can compose of one or more charge units).It is also understood that, where more than one charge unit is used tomake an article, the charge units may have different moldingcompositions.

Several embodiments of the molding process of the present invention aredescribed below:

Process Embodiment 1: Single pressure profile, isothermal

In this method the temperature of the mold is maintained at aessentially constant level throughout the molding cycle. The pressure isincreased to the final molding pressure immediately after closing themold and maintained at that pressure. This method is especially usefulwhere the flash gap of the mold is very small or if the moldingcomposition is highly viscous. Thus, in such applications, it ispreferred where one of the following two conditions should be met: (a)the mold has a flash gap no greater than about 130 microns; or (b) themolding composition has a spiral flow length no greater than about 150cm, preferably no greater than about 100 cm. Additionally, the moldedcomposition should have sufficient hot strength to allow for removal ofthe molded part while still hot without warping or sagging. Thus, themethod generally may not be suitable for making encapsulated parts orparts with very intricate designs.

The first step in the molding process is to provide the mold charge,preferably at room temperature. In some cases, the molding compositionsare prepared in advance and stored at refrigerated temperatures. Thecompositions are generally not malleable enough at the lowertemperatures to be easily used. In addition, the temperature gradient inthe curing part, especially for thick parts, can lead to internal voids.Therefore, if not already at room temperature, the compositions shouldbe warmed to room temperature, by which is meant about 15-30° C.

The second step is to place the room temperature molding composition inthe cavity of a preheated mold. The preheat temperature should besufficient to cause the secondary thermal initiator to pass throughabout 3-10 half lives, preferably about 4-6 half lives, within about tenminutes or less, preferably within about four minutes or less. Thetemperature should also not be so hot as to cause depolymerization or todegrade any of the properties of the molded article. In general, for theacrylic-based compositions of the invention, a temperature in the rangeof from about 100° C. to about 145° C. is useful.

The third step is to close the mold and secure it closed prior topressurization. The mold is preferably closed as soon as possible toprevent volatilization from the mold charge.

The fourth step is to increase the pressure to a selected final moldingpressure. The final molding pressure is selected to maintain theinternal and surface geometric integrity of the molded article. The term“molding pressure” refers to the applied force per unit cross-sectionalarea in the plane of the mold cavity (in units of pounds per squareinch, psi; or kilogram per square centimeter, kg/cm²). By “maintaininternal geometric integrity” it is meant that the pressure is chosen tominimize or avoid internal defects such as shrink marks and voids in themolded article. By “maintain surface geometric integrity” it is meantthat the pressure is chosen to produce on the molded article surfaceessentially the same finish as the machined mold cavity surface. Theexact pressure chosen will depend on the molding composition used andthe desired physical characteristic of the molded article. In general,pressures in the range of from about 500 to about 1500 psi (about 35 toabout 105 kg/cm²) are useful. This step is preferably carried out asquickly as the equipment allows. Often, the third and fourth steps canbe one action.

The fifth step is to maintain the temperature and pressure for a timesufficient to ensure that the secondary thermal initiator has passedthrough about 3-10 half lives, preferably about 4-6 half lives. Thisamount of time is preferably within about ten minutes or less, morepreferably within about four minutes or less.

The sixth step is to reduce the pressure to atmospheric pressure.

The seventh step is to open the mold and remove the molded article.Generally, the molded article is removed without cooling the mold.

Process Embodiment 2: Single pressure, dual temperature profile

In this method two different temperatures are used during the moldingcycle: initially a lower temperature, which is then increased to ahigher temperature. The pressure is increased to the final moldingpressure immediately after closing the mold and maintained at thatpressure. This method can often be used if the flash gap of the mold isvery small or if the molding composition is very stiff. Thus, it ispreferred that one of the following two conditions should be met: (a)the mold has a flash gap no greater than about 1300 microns; or (b) themolding composition has a spiral flow length no greater than about 150cm, preferably no greater than about 100 cm. Because of the dualtemperature profile, the method often can be used for encapsulatingnon-reactive core components and for making parts with intricatedesigns. At the lower temperature, the molding composition can flow tofill the appropriate spaces without completely polymerizing and withoutvolatilizing the monomer(s) and other volatile components. After this,at the higher temperature, the polymerization reactions are completed.

The first step in the method is the same as in the previous method: toprovide the mold charge at room temperature.

The second step is to place the room temperature molding composition inthe mold cavity. The initial mold temperature should be set at mostabout 10° C. lower than the boiling point of the most volatilecomponent. As used herein “the most volatile component” refers anycomponent in the molding composition that has the lowest boiling point.The mold should be set at this initial mold temperature prior toplacement of the mold charge into the mold cavity in order to preventsignificant volatilization of the most volatile component prior to moldclosure. The upper limit for the initial mold temperature is determinedby the molding composition. It is preferred that the mold is preheatedto an initial mold temperature of preferably at least about 50° C. inorder to reduce cycle time. In general, an initial mold temperature inthe range of from about 50 to about 90° C. is useful.

The third step is to close the mold and secure it closed prior topressurization. The mold is preferably closed as soon as possible.

The fourth step is to increase the pressure to a selected moldingpressure as in the fourth step in Process Embodiment 1. Often, the thirdand fourth steps can be one action.

The fifth step, which is carried out concurrently with the fourth step,is to increase the temperature to a temperature which is sufficient toensure that the secondary thermal initiator passes through about 3-10half lives within about ten minutes or less, preferably within aboutfour minutes or less. As discussed above, for acrylic-basedcompositions, a temperature in the range of from about 100° C. to about145° C. is useful. The rate of temperature increase can be adjusted toachieve a desired method cycle time.

The sixth step is to maintain the temperature and pressure for a timesufficient to ensure that the secondary thermal initiator has passedthrough about 3-10 half lives, preferably about 4-6 half lives This stepis to ensure that the polymerization is complete and that the secondarythermal initiator is essentially depleted. Generally, this amount oftime is preferably within about ten minutes or less, more preferablywithin about four minutes or less.

The seventh step is to cool the temperature to the original preheatedtemperature from step (2).

The eighth step is to reduce the pressure to atmospheric pressure.Depending upon the application, the seventh and eighth steps can beperformed concurrently.

The ninth step is to open the mold and remove the molded article.

Process Embodiment 3: Dual pressure profile, isothermal

In this method, the temperature of the mold is maintained at a constantlevel throughout the molding cycle. The pressure is increased to a firstlevel and maintained for a period of time and then increased to a finalmolding pressure for the rest of the molding cycle. This method is oftensuitable for molds with larger flash gaps and for molding compositionswith greater flow.

The first step in the molding process is to provide the mold charge atroom temperature.

The second step is to place the room temperature mold charge in thecavity of a preheated mold. The preheated mold temperature should besufficient to cause the secondary thermal initiator to pass throughabout 3-10 half lives, preferably about 4-6 half lives, in about tenminutes or less, preferably about four minutes or less. The temperatureshould also not be so hot as to cause depolymerization or to degrade ofany of the properties of the molded article. In general, for theacrylic-based compositions of the invention, a temperature in the rangeof from about 100 to about 145° C. is useful.

The third step is to close the mold and secure it closed prior topressurization. The mold is preferably closed as soon as possible.

The fourth step is to increase the molding pressure to an initial levelsufficient to fill the mold with the mold charge. By filling the mold,it is meant that the mold charge is delivered to every volume of themold cavity, including the flash gap. In general, the preferred moldingpressure is from about 100 to about 500 psi (7 to 35 kg/cm²).

The fifth step is to maintain the pressure at this level for an amountof time sufficient to seal the flash gap. Generally, the preferredamount of time is from about 30 to about 90 seconds. By sealing theflash gap, it is meant to allow polymerization of the mold charge to anextent such that the viscosity of the mold charge is sufficient toprevent further mold charge material to pass through the flash gap.

The sixth step is to increase the pressure to a selected moldingpressure to maintain the internal and surface geometric integrity of themolded article. The selected molding pressure should preferably be atleast about 200 psi (14 kg/cm²) greater than the initial moldingpressure.

The seventh step is to maintain the mold at the mold temperature and afinal molding pressure for a time sufficient to ensure that thesecondary thermal initiator has passed through about 3-10 half lives,preferably about 4-6 half lives. Generally, this will be preferablywithin about ten minutes or less, more preferably within about fourminutes or less. This step is performed to ensure that thepolymerization is completed and that the secondary thermal initiator isdepleted. The final molding pressure may be the same as or differentfrom the selected molding pressure.

The eighth step is to reduce the pressure to atmospheric pressure.

The ninth step is to open the mold and remove the molded article withoutcooling the mold.

Process Embodiment 4: Dual pressure profile, dual temperature profile

In this method two different temperatures are used during the moldingcycle and two different pressures. The method is often suitable formolds with larger flash gaps and for molding compositions with greaterflow. As with the Process Embodiment 2, because of the dual temperatureprofile, the method can be used for encapsulating non-reactive corecomponents and for making parts with intricate designs.

The first step in the method is to provide the mold charge at roomtemperature.

The second step is to place the room temperature mold charge in thecavity of a mold having an initial mold temperature that is no greaterthan about 10° C. less than the boiling point of the most volatilecomponent in the composition. Preferably, the mold is preheated. Morepreferably, the mold is preheated to an initial mold temperature of atleast about 50° C. In general, a useful initial mold temperature is fromabout 50° C. to about 90° C.

The third step is to close the mold and secure it closed prior topressurization. The mold is preferably closed as soon as possible.

The fourth step is to increase the temperature to a temperature which issufficient to ensure that the secondary thermal initiator passes throughabout 3-10 half lives, preferably about 4-6 half lives, within about tenminutes or less, more preferably about four minutes or less. Atemperature range of from about 100° C. to about 145° C. is generallyused.

The fifth step is to increase the pressure to an initial levelsufficient to fill the mold with the mold charge as in the fourth stepof Process Embodiment 3.

The sixth step is to maintain the pressure at this level for a timesufficient to effectively seal the flash gap, as in the fifth step ofProcess Embodiment 3.

The seventh step is to increase the pressure to a selected moldingpressure to maintain the internal and surface geometric integrity of themolded article. Preferably, the selected selected molding pressure is atleast about 200 psi (14 kg/cm²) greater than the initial moldingpressure.

The eight step is to maintain the mold at the mold temperature and afinal molding pressure for a time sufficient to ensure that thesecondary thermal initiator has passed through about 3-10 half lives,preferably about 4-6 half lives. The final molding pressure may be thesame as or different from the selected molding pressure in the seventhstep. This amount of time is preferably within about ten minutes orless, more preferably within about four minutes or less. This step is toensure that polymerization is completed and that the secondary thermalinitiator is essentially depleted.

The ninth step is to cool the mold to the original preheated temperaturefrom step (2). The pressure during this cooling step may be different orthe same as the final molding pressure.

The tenth step is to reduce the pressure to atmospheric pressure.Depending upon the application, the ninth and tenth steps can beperformed concurrently.

The eleventh step is to open the mold and remove the molded article.

In the molding processs of the invention, the temperature and pressurecontrol allows for the formation of parts free of both surface andinternal defects. It also allows for low cycle times with minimal partshrinkage, which lowers the manufacturing cost. The use of the coolcharging temperature (Process Embodiments 2 and 4) allows parts to bemade without material knit lines which result from monomer volatility.It also allows easier production of parts free of surface defects. Theuse of dual pressure profiles (Process Embodiments 3 and 4) allows theuse of low viscosity compositions and minimization of part shrinkage.

It is understood that those embodiments of the present inventionemploying a “dual pressure profile” may employ intermediate pressuresteps as well. By “intermediate pressure,” it is meant a pressure duringthe molding process that is other than the initial and the final moldingpressures. Similarly, it is understood that those embodiments of thepresent invention employing a “dual temperature profile” may also employsteps at intermediate temperatures. By “intermediate temperature,” it ismeant a temperature during the molding process that is other than theinitial and the final molding temperature

Process Embodiments 5-8: Intricate Design Method

The present invention also relates to a method for making an articlehaving at least one intricate design detail. In a preferred embodiment,this method is performed using the general steps of any one of ProcessEmbodiment 1 through 4. The general steps of Process Embodiment 3 orProcess Embodiment 4 can be especially useful for making articles havingintricate design details using lower viscosity molding compounds as moldcharges. The dual pressure profile of Process Embodiments 3 and 4 may beuseful for not only avoiding flashing the molding compound out of theflash gap, but also to allow application of increased pressures tofollow polymerization shrinkage and prevent internal voiding, shrinksink areas, and other internal and external defects in the moldedarticle.

Regardless of which of the Process Embodiment general steps are used,the mold charge is preferably first preformed into a single unit chargeor into multiple unit charge consistent with the dimensions of the moldcavity. Preforming generally provides advantages such as the following:(1) it minimizes the material flow distance within the mold; (2) itminimnizes the amount of monomer offgassing from the molding compound asthe mold closes and fills. As used herein, “offgassing” refers tovolatilization from the molding compound, which results in the formationof dry spots on the finished article. After preforming the mold charge,it is placed in the mold cavity, preferably as quickly as possible.Especially for making articles having multiple intricate design details,several different shapes or dimensions may be needed to sufficientlycharge the mold. Once the mold is charged, it should be closed withoutdelay and the molding cycle is continued as described in any one ofProcess Embodiments 1 through 4.

Particularly in compression molding, the operating conditions of ProcessEmbodiment 2 are preferred for making articles containing intricatedesigns because the lower charging temperature removes or reduces thelevel of monomer offgassing at the point of contact between the moldingcompound and the warmed surface of the mold cavity.

Particularly in the cases of transfer or injection molding, the chargepreforming is not critical. The unpreformed ingot of molding compositioncan be cut and introduced into the mold, which does its own preformingvia transfer cylinders or injection screws. While a cooler “charging”temperature may or may not be useful in these methods, it could increasecycle time.

Process Embodiments 9-12: Encapsulation Method

The compositions and methods of the invention are also suitable for theencapsulation of non-functional materials. By “non-functional materials”is meant materials which take up volume, may impart a desirableaesthetic, but do not impart a new functional capability in the moldedarticle. Examples of non-functional materials include sheet materials ofwood products, such as particle board; filled and unfilled polymers;decorative surface materials such as Corian® solid surface materials;recycled plastics; and others. Such materials may be encapsulated by thecompositions of the invention to achieve the aesthetics of solid surfacematerials at a lower cost. Part features, such as screw inserts, can beencapsulated by the molding composition, as well, resulting in integralhardware in the parts. Such parts are also hermetically sealed andresistant to environmental effects, such as humidity.

In addition, metal and metal/plastic composites can be encapsulated toprovide good heat transfer for the surface materials. Fiber mats orcloth of glass or organic polymers, such as polyaramids, can beencapsulated to provide structural reinforcement and/or flameretardancy. Honeycomb structures can be encapsulated to produce articlesof reduced weight. Such encapsulated articles are conveniently producedby injection molding, however, compression and transfer moldingtechniques can also be used.

The compositions and processes of the invention are also useful for theencapsulation of functional inserts. By “functional insert” is meant amaterial which imparts a new use or function to the article. Such newuse may be heating or cooling, electrical, plumbing, sound dampening,providing a firewall, making the article penetration-resistant orpenetration-proof, among others. Examples of suitable functional insertsinclude electrical parts, light emitting materials, heated resistancewires, electronic wiring, plumbing units, heating and cooling coils, andmany others. Such encapsulated articles are also conveniently producedby injection molding, however, compression and transfer moldingtechniques can also be used.

The present invention further relates to an method for making a articleincluding at least one encapsulated core. Encapsulation can be achievedusing compression molding, preferably following the general steps ofProcess Embodiment 1 or 2 above; or using transfer or injection molding,preferably following the general steps of Process Embodiment 3 or 4above.

When compression molding is used for encapsulating a core, theencapsulant core is preferably sandwiched between at least two preformedcharges of molding compound in a “composite” charge. This charge may bejoined by secondary charges to fully charge the mold as outlined abovein any one of Process Embodiment 1 through 4. The encapsulant core maybe held in place by hardware inserted into (or a part of) theencapsulant, by pins which are an integral part of the mold design, orby the thickness and homogeneity of the equal preformed chargesthemselves. The mold is closed and cycled with the same considerationsas above in Process Embodiment 1 or 2.

In encapsulating a core using transfer or injection molding, the core ispreferably introduced into the mold cavity and held in place either bythe design of the encapsulant itself or by design elements of the moldsuch as, for example internal pins or fixtures. The mold charge can beintroduced into the mold via injection where the molding compound isforced into the mold, encapsulating the inserted core. The mold isclosed and cycled according to the general steps described in ProcessEmbodiment 3 or 4.

The nature of the encapsulant, such as the impurities contained in theencapsulant, often affects the method chosen to carried out the molding.For example, a steel sheet encapsulant generally would not expand duringthe molding process. Therefore, any of the above-described ProcessEmbodiment 1 through 4 may be suitable for making a molded articleencapsulating the steel sheet. In contrast a particle board encapsulantgenerally may contain moisture that may vaporize during the moldingprocess. Therefore, Process Embodiments 2 and 4 may be more suitable formaking a molded article encapsulating the particle board.

It is understood that the present invention is moreover directed to amethod for making an article having at least one core encapsulatedtherein and at least one intricate design on the article surface, whichmethod preferably includes a combination of the general steps describedin any one of Process Embodiments 5 through 8 with the general stepsdescribed in any one of Process Embodiments 9 through 12.

Finishing

Finishing concerns in molded products are generally fairly minor versusthose encountered in cast products. The finish surface of the moldedpart is largely dictated by the finish of the machined mold. Finishingof molded parts primarily involves removal of the flashing or residualpolymerized compound which accumulates at gaps in the mold such as moldparting lines, ejection pins, and sliders. This is removed by lightsanding or milling to provide the finished part. In some cases, surfacedefects are observed in molded parts due to mold design or mold finishissues; such defects must be removed, if possible, by sanding andpolishing.

The compositions and processes of the invention are also suitable forproducing articles in which the molding material is on at least a partof one or more, but not all surfaces of a substrate. In such articles,the substrate is not completely encapsulated by the molding material.The substrate can be a flat sheet with a sheet of molding compositionoverlying all or part of one side. Such molded structures can haveadvantages in terms of adhesion and strength when compared to laminatedstructures which are glued together. In some cases, the substrate willbe prestressed prior to molding to prevent distortion in the finalmolded article arising from time and/or shrinkage forces. Alternatively,the molding composition can be molded onto two or four sides of a flatsubstrate, leaving the sides and/or ends exposed. In addition, athree-dimensional shape can be molded onto a flat substrate, a flatsheet can be molded onto a three-dimensional substrate, and a threedimensional shape can be molded onto a three-dimensional substrate. Itwill be clear that there are a variety of molding options in which themolding composition is molded onto all or part of a substrate. Examplesof suitable substrates include wood, metal, woven and nonwoven fibermats, clths, and veils, clear polymeric materials, filled polymericmaterials, honeycomb structures and others. Combinations of substrates,including composites substrates, can also be used. An unfilled acrylicsheet is particularly suitable as a substrate for either a sheet moldedmaterial or a shaped molded material. Alternatively, a woven or nonwovenfiber mat may be impregnated into the molded article for structuralreinforcement and/or as a structural barrier.

The compositions and methods of the invention are also suitable forproducing articles in which the molding material is on only one surfaceof a substrate. Examples of suitable substrates include wood, metal,clear polymeric sheets, honeycomb structures and others. In some cases,the substrate will be prestressed to prevent distortion in the finalmolded article arising from time and/or shrinkage forces. Alternatively,a nonwoven or woven fiber mat may be impregnated into the molded articlefor structure reinforcement and/or as a structural barrier.

The molding processes of the present invention produce molded articlesrequiring fewer finishing steps when compared to articles made fromcasting processes. The molding processes have low cycle times and resultin products which are robust. The molding methods of the presentinvention are especially suitable for high volume production of highquality engineered parts. When acrylic-based molding materials are used,the products made from the composition and methods of the invention havethe aesthetic appearance of filled acrylic materials. They further haveother advantages associated with filled acrylic materials, such as UVstability, opacity, hardness, repairability, inconspicuous seaming,stain resistance and fabricability.

Aspects of the present invention are shown by the following examples forpurposes of illustration. These examples and embodiments are not meantto limit the invention in any way. Those skilled in the art willrecognize that charities, additions, and modifications may be made, allwithin the spirit and scope of the invention and how it relates to theproduction of new functionalities and aesthetics for the sold surfacesindustry.

EXAMPLES

Various components of the molding compositions used in Examples 1-22 aredescribed below:

Acrylic sirup

A reactive acrylic sirup composed of 15-25% by weight of anon-crosslinked polymer resin dissolved in a monomer solution wasprepared by either (1) partially polymerizing an acrylic monomer mixtureor (2) dissolving one or more acrylics resins in one or more acrylicmonomers.

In the former case (1), a sirup comprising 24% polymethylmethacrylate(Mn approx. 32,000) dissolved in methylmethacrylate was prepared bypartial polymerization of methylmethacrylate using2,2′-azobis(isobutyronitrile) initiator [supplied by VAZO 64 from E.I.du Pont de Nemours and Company] in a continuous reactor process.

In the latter case (2), such a sirup was prepared by dissolving one ormore of the following acrylic resins in MMA at 3-24 wt % solids:

V045 acrylic resin 99.5% poly(methylmethacrylate/ethyl acrylate), Mn >60,000; supplied by ATOHAAS, Philadelphia, PA; Elvacite ® 2014 resin98-100% poly(methylmethacrylate/2- ethylhexyl acrylate/methacrylicacid), Mn > 70,000; supplied by ICI Acrylics Inc., Wilmington, DE

Soluble, poly-(meth)acrylic-functional oligomeric species was also beincluded in sirup formulations. Polymerization inhibitors such asmethylhydroquinone (MEHQ) were added as needed.

Initiators

The Examples employed one of the primary thermal initiators listedbelow:

Lupersol 10M75 t-Buytl Peroxyneodecanoate supplied as a 75% solution inOMS (Odorless Mineral Spirit) by Elf Atochem (King of Prussia, PA); tenhour half life temperature of 48° C.; or Lupersol 11 t-ButylPeroxypivalate supplied as a 75% solution in OMS by Elf Atochem; tenhour half life temperature of 58° C.

The secondary thermal initiator employed was2,2′-azobis(methylbutyronitrile) supplied as a 100% solid by DuPont(Wilmington, Del.) under the tradename VAZO 67, with a ten hour halflife temperature of 67° C.

Alumina Trihydrate (ATH)

The ATH fillers listed in Table 1 below were used in the Examples:

TABLE 1 ATH fillers d50 particle size ATH filler(s) (microns)* Supplieruntreated ATH 36 ALCAN (Quebec, Canada) untreated ATH or 11 SOLEM(China) A174 silane-treated ATH A174 silane-treated 47 Nippon LightMetals (Japan) ATH *Particle sizes and particle size distributions weremeasured using a Leeds & Northrup Microtrac FRA Instrument.

Decorative Filled Acrylic Particles (DFAP's)

Decorative filled acrylic particles were prepared from ATH-filled PMMAby milling and/or grinding to the desired extent. The materialcomposition is characteristically 55-65% ATH by weight and containspigments to achieve the desired color. The particle sizes were thenseparated by sieve into fractions. These fractions were combined invarious ratios needed to achieve the desired aesthetic pattern effect inthe molded article. Combined fractions of different colors were used toachieve the desired color effect in the molded article.

Setting Agent

Polymer particle setting agents employed in the Examples are listed inTable 2 below:

TABLE 2 Polymer Particle Setting Agents d50 Particle Size AvailableSetting Agent Composition (microns)* from PARALOID ® 99-100%poly(methyl- 122 Rohm and Haas K-120 methacrylate/ethyl Company, N-Dacrylate) Philadelphia, PA Kane Ace >98% poly(methyl- 150-190 KanekaTexas FM-25 methacrylate/acrylic) Corporation. core/shell copolymerPasadena, TX Kane Ace >98% poly(methyl- 150-190 Kaneka Texas FM-20methacrylate/acrylic) Corporation. core/shell copolymer Pasadena, TXElvacite ® >99%  7-130 ICI Acrylics Inc., 2896 polymethyl- Wilmington,DE methacrylate Elvacite ® [>99% 150 ICI Acrylics Inc. 2041 polymethyl-methacrylate *Particle sizes and particle size distributions weremeasure using a Leeds & Northrup Microtrac FRA Instrument.

Composite polymer/filler particle setting agents employed in theExamples were: filled acrylic particles generated from the milling,sawing and sanding of Corian® ATH-filled acrylic polymer solid surfacematerials; d50 of 60 microns. Particle sizes and particle sizedistributions were measured using a Leeds & Northrup Microtrac FRAInstrument.

Unless otherwise stated, all mixing steps were performed at roomtemperature. For those mixing steps that employed a water-cooled mixingcavity, the mixing temperature was between about 10° C. to about 15° C.

Additional materials employed in this 4work are straightforward to thoseskilled in the art and are described below in specific examples.

Spiral flow length measurement

The spiral flow length is related to viscosity and measured undermolding conditions. A spiral flow method using a test mold manufactureby the Atlantic Tool & Die Company (S. Plainfield, N.J.) was used in theExamples

This spiral mold has the following dimensions: 75 inch (190.5 cm) long;0.375 inch (0.95 cm) wide; 0.125 inch (0.32 cm) deep; with a plungerdiameter of 2⅜ inch (6.03 cm). The bottom half of the mold is graded in0.25 inch (0.635 cm) increments.

The technique used a transfer mold in which the molding composition isforced out of the transfer cylinder and into a spiral runner under thepressure and temperature conditions to be used in the moldingapplication. A charge of from about 50-100 g of molding composition wasplaced in the transfer cylinder of the mold which has been preheated toa temperature of from about 125° C. The mold was then closed with aclamping pressure of from about 500 psi (42.2 kg/cm²). The mold wasopened after about 3 minutes and the molded part was ejected. Themaximum flow distance was then measured by reading the imprinted scaleon the bottom of the part.

Example 1 Preparation of Molding Compound

A liquid mixture having the components listed in Table 3 below wasprepared.

TABLE 3 Example 1 Liquid Mixture Component Parts by Weight Acrylicsirup, 24% V046 solids in MMA 705 Ethylene glycol dimethacrylate 32.2Lupersol 11 3.2 VAZO 67 0.5 Zelec MO 2.9 Black Pigment Dispersion 3.0

The liquid mixture was mixed to ensure homogeneity. The black pigmentdispersion employed was a 5% solids dispersion of carbon black inepoxidized soybean oil used as furnished by RBH Dispersions, Boundbrook,N.J.

The solid materials listed in Table 4 below were introduced into aconstant rpm 1.5 gallon double arm sigma blade mixer (Baker-Perkins) andpremixed for 1 minute:

TABLE 4 Example 1 Solid Materials Component Parts by Weight ATH; NLMsilane-treated 1950 Rohm & Haas K120ND 366 Zinc Stearate 4.5

The liquid mixture was added and the molding compound was mixed for 8minutes at which point the material transformed into a thick moldingcompound of uniform composition. The molding compound was removed fromthe mixer and packaged in bulk form in an airtight plastic bag. Thecompound was then stored at 5-10° C.

Within 24 hours of mixing, the molding compound consistency andperformance was evaluated using a spiral flow mold at 125° C. with anapplied pressure of 500 psi. Under these conditions, the flowlength fellbetween 31″ (78.7 cm) and 34″ (86.4 cm).

Example 2 Isobaric/Isothermal Molding Process of Example 1 Composition

The molding compound of Example 1 was evaluated by compression moldingin a 10″×10″ (25.4 cm×25.4 cm) test mold constructed of steel, designedwith a flash gap of 0.001″ (25 micron), and having internal electricheater units. The mold was preheated to 125° C. and a 1040 g charge ofmolding compound was placed in the cavity. The mold was closed and apressure of 800 psi (56.4 kg/cm²) applied. After 5 minutes, the mold wasopened and the resulting plaque removed.

Although the resulting molded plaque presented excellent reproduction ofthe mold surface and dimension, it also showed surface defectsassociated with monomer boiloff prior to mold closure. These detects aresurface in nature and are manifested as whitened, microvoided areas onthe bottom of the part where the molding charge was in contact with thehot mold prior to mold closure. Physical properties of the moldedmaterial are shown in Table 5 below in comparison with typical valuesfor a Corian® Genesis Pearl Gray continuous cast filled acrylic solidsurface material.

TABLE 5 Comparative Physical Properties Corian ® Genesis Ex. 1 PearlGray Flexural Energy to Break (in-lb) 2.80 3.50 Flexural % Strain atBreak 0.96 0.99 Rockwell M hardness 84 90 Maximum Impact Energy (in-lb)6.77 7.98 [0.25″ (0.64 cm) thickness]

Example 3 Isobaric/Temperature Profile Molding Process of Example 1Composition

The molding compound of Example 1 was evaluated using a mold chargingtemperature of 80° C. The 1040 g charge was introduced into the moldcavity and the mold was closed. Immediately, the applied pressure wasincreased to 800 psi (56.4 kg/cm²) and the mold temperature wasincreased to 125° C. Three minutes after the mold temperature reached125° C., the mold was opened and the resulting plaque removed. Thewhitened surface defects observed in Example 1 were not present.

Example 4 Use of Smaller Particle Size ATH in Example 1 Composition

The molding compound of Example 1 was reproduced substituting thesilane-treated Solem ATH for the NLM silane-treated ATH. The mixingcharacter was identical as was the moldability of the resulting moldingcompound. The resulting material exhibited improved physical propertieswhile maintaining aesthetic appearance. Physical data are listed inTable 6 below.

TABLE 6 Flexural Energy to Break (in-lb) 4.84 Flexural & Strain at Break1.37 Rockwell M Hardness 87

Example 5 Calcium Carbonate Filter Substituted for ATH in Example 1Composition

The molding compound of Example 1 was reproduced substituting calciumcarbonate (Polar Minerals, Mt. Vernon, Ind.) for the NLM silane-treatedATH. Also, a sirup (nominally 24% solids) prepared via industrial scalepartial polymerization of MMA using 2,2′-azobis(2-methylpropanenitrile)[sold as VAZO 64 by DuPont Company, Wilmington Del.] as thermalinitiator was employed. The mixing behavior of this formulation wassomewhat more difficult, taking more time to achieve even mixing.Moldability of the resulting molding compound was similar to the above.As expected the molded plaque exhibited a more opaque appearance ascompared to that of Example 1. Physical data are listed in Table 7below:

TABLE 7 Flexural Energy to Break (in-lb) 2.40 Flexural & Strain at Break0.99 Rockwell M Hardness 86

Example 6 Dacron® Fiber as Setting Agent and Reinforcement

The molding compound of Example 1 was reproduced using the followingmixture of solids components listed in Table 8 below:

TABLE 8 Solid Components Component Parts by Weight ATH; NLMsilane-treated 1950 Rohm & Haas K120ND 210 0.125″ Dacron ® fiber 90 ZincStearate 4.5

Also, a sirup (nominally 24% solids) prepared via industrial scalepartial polymerization of MMA using 2,2′-azobis(2-methylpropanenitrile)[sold as VAZO 64 by DuPont Company, Wilmington, Del.] as thermalinitiator was employed. The liquid mixture was added to the abovemixture after mixing for 1 minute. The molding compound was mixed for 7minutes before it was removed from the mixer and packaged. Due to theMMA-absorptive nature of the Dacron® fiber, the material achieved asimilar viscosity. The molding compound was evaluated using the 10″×10″test mold and the isothermal/isobaric pressing profile described inExample 1. Upon molding, very little flash was observed. It appearedthat the swollen polyester fiber aided in sealing the mold cavity in theearly stages of the molding process. Although flexural propertiesremained unchanged, the presence of the fiber reinforcement preventedcatastrophic failure (shatter) in flexural and impact measurements.

Example 7 Formulation Without Noncrosslinked Polymer Resin

A liquid mixture was introduced into a water cooled 2.5 gallon doubleplanetary mixer (Charles Ross & Son Company; Hauppauge, N.Y.). Theliquid mixture contained the components listed in Table 9 below:

TABLE 9 Liquid Mixture Component Parts by Weight MMA 540 Ethylene glycoldimethacrylate 32.4 Lupersol 11 3.2 VAZO 67 0.5 Zelec MO 8.4 BlackPigment Dispersion 3.0

This liquid mixture was mixed to ensure homogeneity. The black pigmentdispersion employed was a 5% solids dispersion of carbon black inepoxidized soybean oil used as furnished by RBH Dispersions, Boundbrook,N.J. To this mixture was added the components listed in Table 10 below,in the order listed:

TABLE 10 Component Parts by Weight Zinc Stearate 4.5 ATH; NLM,silane-treated 1950 Rohm & Hass K120ND 465

The zinc stearate was mixed with the liquids for 5 minutes. The ATH wasadded and the mixture was mixed for an additional 5 minutes to ensureeven wetting. The Rohm & Haas K120ND was then added at high mixer rpm,forming a dry mixture which coalesced into a stiff molding compoundwithin three minutes. The compound was then mixed for an additionaltwenty minutes under a 25″ Hg vacuum (735 mm Hg). The molding compoundwas removed from the mixer and packaged in bulk form in an airtightplastic bag. The compound was then stored at 5-10° C.

The molding compound was evaluated using the 10″×10″ test mold and theisothermal/isobaric pressing profile described in Example 1. Physicaldata is presented in Table 11 below:

TABLE 11 Flexural Energy to Break (in-lb) 3.45 Flexural % Strain atBreak 1.06 Rockwell M Hardness 80

Example 8 Formulation Employing Decorative Fillers

A liquid mature containing the components listed in Table 12 below wasprepared. The liquid mixture was introduced into a water cooled 2.5gallon double planetary mixer (Charles Ross & Son Company; Hauppauge,N.Y.):

TABLE 12 Liquid Mixture Component Parts by Weight Acrylic sirup, 24%V045 solids 711 Ethylene glycol dimethacrylate 32.4 Lupersol 11 3.2 VAZO67 0.5 Zelec MO 3.2

This liquid mixture was mixed to ensure homogeneity.

The following solid materials listed in Table 13 below were premixed andintroduced together into the mixer:

TABLE 13 Solid Components Component Parts by Weight ATH - NLMsilane-treated 1436 Rohm & Haas K120ND 120 Zinc Stearate 4.5

The mixture was mixed for 2 minutes at which point the materialtransformed into a paste. A mixture of decorative ATH-filled acrylicparticles (DFAP's) within the size range of 30 to 150 mesh (approx.100-560 microns) was added and mixed in:

DFAP's 690 parts by weight

The mixture divas mixed for 15-20 minutes under 25″ Hg vacuum (735 mmHg) during which the material transformed into a thick molding compoundof uniform composition. The molding compound was removed from the mixerand packaged in bulk town in an airtight plastic bag. The compound wasstored at 5-10° C.

Within 24 hours of mixing, the molding compound consistency wasevaluated using a spiral now mold at 125° C. and an applied pressure of500 psi. Under these conditions, the flowlength falls between 28″ (71.1cm) and 32″ (81.3 cm).

Example 9 Isobaric/Isothermal Molding Process of Example 8 Composition

The molding compound was also evaluated by compression molding in the10″×10″ test mold described in Example 1. The mold was preheated to 125°C. and a 530 g charge of molding compound was placed in the cavity. Themold was closed and a pressure of 800 psi (56.4 kg/cm²) applied. After 5minutes, the mold was opened and the resulting plaque removed.

Although the resulting molded plaque presented excellent reproduction ofthe mold surface and dimension, it also showed surface defectsassociated with monomer boiloff prior to mold closure. These detects aresurface in nature and are manifested as whitened, microvoided areas onthe bottom side of the part where the molding charge was in contact withthe hot mold prior to mold closure. The molded article has a uniformgranite-like appearance exhibiting a translucent visual depth. Physicalproperties of the molded material are shown in Table 14 below incomparison with typical values for Corian® Sierra Dusk continuous castfilled solid surface material.

TABLE 14 Comparative Physical Data Corian ® Sierra Ex. 8 Dusk MaterialFlexural Energy to Break (in-lb) 3.04 3.38 Flexural % Strain at Break0.99 1.05 Rockwell M hardness 84 91 Maximum Impact Energy (in-lb) 7.645.68 [0.25″ (0.64 cm) thickness]

By gas chromotagraphy analysis the overall residual MMA was measured0.62% by weight of the polymerized sample. This translates to 3.4% ofthe amount of monomers present in the original molding composition.

Example 10 Isobaric/Temperature Profile Molding Process of Example 8Composition

The molding compound of Example 8 was evaluated using a mold chargingtemperature of 80° C. A 1040 g charge was introduced into the moldcavity and the mold was closed. Immediately, the applied pressure wasincreased to 800 psi (56.4 kg/cm²) and the molt temperature wasincreased to 125° C. Three minutes after the mold temperature reached125° C., the mold was opened and the resulting plaque removed. Thewhitened surface defects observed in Example 8 were not present.

Example 11 Effect of Increasing Amounts of Crosslinking Agent in Example8 Composition

The effect of crosslinking agent on the hot strength of the moldedarticle was evaluated by altering the level of crosslinking agent in themolding compound.

Two compositions (A and B) were prepared. The liquid mixtures ofComposition A and B are listed in Table 15 below. Each of the two liquidmixtures was introduced into a separate water-cooled 2.5 gallon doubleplanetary mixer (Charles Ross & Son Company; Hauppauge, N.Y.):

TABLE 15 Liquid Mixture Components Composition A Composition B (Parts(Parts Components by Weight) by Weight Acrylic sirup, 24% V045 solids732 691 Ethylene glycol 11.1 52.5 dimethacrylate Lupersol 11 3.3 3.2VAZO 67 0.6 0.5 Zolec MO 3.2 3.2

Each liquid mixture was mixed to ensure homogeneity.

The solid materials listed in Table 16 below were premixed andintroduced into the mixer for each of the two liquid mixtures:

TABLE 16 Solid Components for Compositions A and B Component Parts byWeight ATH - NLM, silane-treated 1436 Rohm & Haas K120ND 120 ZincStearate 4.5

The mixture was mixed for 3 minutes at which point the materialtransformed into a paste. A mixture of decorative ATH-filled acrylicparticles (DFAP's) within the size range of 30 to 150 mesh (approx.100-560 microns) was added to each composition and mixed in:

Component Parts by Weight DFAP's 690

The mixture was mixed for 15-20 minutes under 25″ Hg vacuum (735 mm Hg)during which the material transformed into a thick molding compound ofuniform composition. The molding compound was removed from the mixer andpackaged in bulk form in an airtight plastic bag. The compound wasstored at 5-10° C.

The molding compounds were evaluated versus the formulation of Example 8using the 10″×10″ mold described in Example 1. The mold was preheated to125° C. and a charge of molding compound sufficient to create a 0.25″(0.64 cm) thick molded plaque was placed in the cavity. The mold wasclosed and a pressure of 800 psi (56.4 kg/cm²) applied. After 5 minutes,the mold was opened and the resulting plague was removed hot using theinternal ejector pins. After cooling, the molded plaques were examinedfor deformation and whitening in the ejector pin contact areas.

The plaque prepared from formulation A above showed significantdeformation and whitening, even on the top surface of the plaque. Theplaque prepared from the formulation of Example 8 showed minordeformation and slight whitening on the lower surface. The plaqueprepared from formulation B above showed no visible deformation orwhitening. Therefore, the formulation B plaque exhibited the highest hotstrength upon removal of the article from the mold.

An instrumented impact analyzer, INSTRON DYNATUP Model 8250 availablefrom Instron, was used to measure the maximum impact energy of thesamples from the molded articles made from formulations A, B and Example8 composition. The sample dimensions were 4 by 4 by 0.25 inches.

The instrumented impact data are shown in Table 17 below.

TABLE 17 A Ex. 8 B Maximum Impact Energy (in-lb) 8.21 7.64 7.22 [0.25″(0.64 cm) thickness]

Example 12 Effect of Crosslinking Agent Character on Hot Strength andPhysical Properties

The effect of crosslinker character on physical properties and moldedarticle hot strength was demonstrated through use of an aliphaticurethane polymethacrylate oligomer. This material was supplied by theSartomer Company (Exton, Pa.) as CN1963, a 75% solution of oligomer intrimethylolpropane trimethacrylate.

A liquid mixture was prepared. Components of the liquid mixture arelisted in Table 18 below. The liquid mixture was introduced into awater-cooled 2.5 gallon double planetary mixer (Charles Ross & SonCompany; Hauppauge, N.Y.):

TABLE 18 Liquid Mixture Component Parts by Weight Acrylic sirup, 24%VO45 solids 668 CN1963 77 Lupersol 11 3.0 VAZO 67 0.5 Zelec MO 3.2

The liquid mixture was mixed to ensure homogeneity.

The solid materials listed in Table 19 below were premixed andintroduced into the mixer:

TABLE 19 Solid Components Component Parts by Weight ATH - NLM,silane-treated 1437 Rohm & Haas K120ND 120 Zinc Stearate 4.5

The mixture was mixed for 3 minutes at which point the materialtransformed into a paste. A mixture of decorative ATH-filled acrylicparticles (DFAP's) within the size range of 30 to 150 mesh (approx.100-560 microns) was added and mixed in:

Component Parts by Weight DFAP's 690

The mixture was mixed for 15-20 minutes under 25″ Hg vacuum (735 mm Hg)during which the material transformed into a thick molding compound ofuniform composition. The molding compound was removed from the mixer andpackaged in bulk form in an airtight plastic bag. The compound wasstored at 5-10° C.

The molding compound was evaluated using the 10″×10″ mold described inExample 1. The mold was preheated to 125° C. and a charge of moldingcompound sufficient to create a 0.25″ (0.64 cm) thick molded plaque wasplaced in the cavity. The mold was closed and a pressure of 800 psi(56.4 kg/cm²) applied. After 5 minutes, the mold was opened and theresulting plaque was removed hot using the internal ejector pins. Theresulting molded article was found to have excellent hot stregnth.Instrumented impact tessting measured a maximum impact energy of 7.7in-lbs.

Example 13 Use of FAP's as Setting Agent

A liquid mixture having the components listed in Table 20 below wasprepared. The liquid mixture was introduced into a water-cooled 2.5gallon double planetary mixer (Charles Ross & Son Company; Hauppauge,N.Y.):

TABLE 20 Liquid Mixture Component Parts by Weight Acrylic sirup, 24%V045 solids 1019 Ethylene glycol dimethacrylate 13.0 Lupersol 10M75 3.3VAZO 67 0.8 Zelec MO 4.1

This liquid mixture was mixed to ensure homogeneity.

The solid materials listed in Table 21 below were premixed andintroduced into the mixer:

TABLE 21 Solid Components Component Parts by Weight ATH - ALCAN,non-treated 1960 FAP's 200

The mixture was mixed for 3 minutes at which point the materialtransformed into a paste. A mixture of decorative ATH-filled acrylicparticles (DFAP's) within the size range of 30 to 150 mesh (approx.100-560 microns) was added and mixed in:

Component Parts by Weight DFAP's 800

The mixture was mixed for 20 minutes under a 25″ Hg vacuum (735 mm Hg)during which the material transformed into a thick molding compound ofuniform composition. The molding compound was removed from the mixer andpackaged in bulk form in an airtight plastic bag. The compound wasstored at 5-10° C.

The resulting molding compound was molded using a steel hand mold thigha 6″ (15.24 cm) diameter cavity which molds a 0.5″ (1.27 cm) thick part.The mold cavity was preheated to about 80° C. by placing the moldbetween 125° C. press platens. The mold was charged and returned to thepress and placed under 1000 psi (70.45 kg/cm²) for 6 minutes duringwhich time the external mold temperature reached 118° C. for a period ofat least 3 minutes. The platens were then water cooled until theexternal mold temperature reached about 80° C. whereupon the maid wasremoved and opened. The molded plaque showed excellent surface quality.Selected physical properties are an shown in Table 22 below:

TABLE 22 Flexural Energy to Break (in-lb) 2.5 Flexural % Strain at Break0.80

Example 14 Molding Compound Composition Using Core/Shell Latex SettingAgent

A liquid mixture having the components listed in Table 23 below wasprepared. The liquid mixture was introduced into a water-cooled 2.5gallon double planetary mixer (Charles Ross & Son Company; Hauppauge,N.Y.):

TABLE 23 Liquid Mixture Component Parts by Weight Acrylic sirup, 20%V045 solids 1300 Ethylene glycol dimethacrylate 16.6 Lupersol 10M75 4.2VAZO 67 1.0 AOT-S 1.6 Zelec MO 4.2

This liquid mixture was mixed to ensure homogeneity.

The following solid materials listed in Table 24 below were premixed andintroduced into the mixer:

TABLE 24 Solid Components Component Parts by Weight ATH - ALCAN,non-treated 2525 Kaneka FM-25 225

The mixture was mixed for 3 minutes at which point the materialtransformed into a paste. A mixture of decorative ATH-filled acrylicparticles (DFAP's) within the size range of 30 to 150 mesh (approx.100-560 microns) was added and mixed in:

Component Parts by Weight DFAP's 950

The mixture was mixed for 10 minutes under 25″ Hg vacuum (735 mm Hg)during which the material transformed into a thick molding compound ofuniform composition. The molding compound was removed from the mixer andpackaged in bulk form in an airtight plastic bag. The compound wasstored at 5-10° C.

Example 15 Encapsulation of Particle Board Insert with Example 14Composition

A particle board insert was prepared from 0.625″ stock with dimensions 9625″×9.625″. Screw inserts were placed into the particle board in eachcorner, two inches from each side. The holes of each insert were pluggedwith a urethane foam material. Strips of Black Pearl Corian® (DuPontCompany, Wilmington, Del.) with cross sectional dimension 0.25″×0.25″were centered and fastened onto the edges of the particle board using acommercial cyanoacrylate adhesive.

Two charges of the above formulation, each weighing 603 g, were eachprepressed into a uniform thickness, circular charge about 9″ indiameter. The particle board insert was sandwiched between the chargesto create a composite charge. The composite charge was placed into aroom temperature 10″×10″ aluminum frame hand mold having a 0.005″ (127micron) flash gap. The mold was closed and placed into a hydraulic pressat a platen temperature of 140° C. A pressure of 250 psi (17.6 kg/cm²)was initially applied to fill the mold. Pressure was gradually increasedto 550 psi (38.7 kg/cm²) over 3.5 minutes. Pressure and heat wereapplied for 8 minutes during which time the external mold temperaturereached 115° C. for a period of at least two minutes. The mold was thenplaten-cooled under pressure until the external mold temperature reachedabout 80° C. The pressure was then released and the mold was removed andopened. The molded article was removed from the mold and the urethanefoam was removed from the screw insert holes.

The resulting molded article was therefore comprised of an encapsulatedparticle board insert and had a molded-in edge band and molded-in screwinserts. Both the edge band and the screw inserts were integrally bondedto the molded material. The molded article showed excellent quality andrepresents a ready for use composite pan.

Upon evaluation, is was found that the polymerizable fraction of themolding compound permeated the insert material for a distance of up to0.25″ (0.63 cm) into the insert material. This was found to greatlyenhance the impact properties of the article versus the fastening ofsimilar sold surface material to particle board using commercialadhesives.

Example 16 Encapsulation of Thermoplastic Sheet Insert with Example 14Composition

An insert was prepared from 0.5″ thick extruded recycled PVC material.Two charges of the formulation of Example 14, each weighing 603 g, wereeach prepressed into a uniform thickness, circular charge about 9″ indiameter. The insert was sandwiched between the charges to create acomposite charge. The composite charge was placed into a roomtemperature 10″×10″ aluminum frame hand mold having a 0.005″ (127micron) flash gap. The mold was closed and placed into a hydraulic pressat a platen temperature of 140° C. A pressure of 250 psi (17.6 kg/cm²)was initially applied to fill the mold. Pressure was gradually increasedto 550 psi (38.7 kg/cm²) at 3.5 minutes. Pressure and heat weremaintained for 8 minutes during which time the external mold temperaturereached 115° C. for at least two minutes. The mold was then platencooled under pressure until the external mold temperature reached about80° C. The pressure was then released and the mold was removed andopened. The molded article was removed from the mold and was comprisedof an encapsulated PVC board insert. The molded article showed excellentquality and represents a ready for use composite part.

Example 17 Encapsulation of Nomex® Paper Sheet

A liquid mixture having components listed in Table 25 below wasprepared. The liquid mixture was introduced into a water-cooled 2.5gallon double planetary mixer (Charles Ross & Son Company; Hauppauge,N.Y.):

TABLE 25 Liquid Mixture Component Parts by Weight Acrylic sirup, 20%VO45 solids 765 Ethylene glycol dimethacrylate 9.8 Lupersol 10M75 2.4VAZO 67 0.6 AOT-S 1.0 Zelec MO 2.5

This liquid mixture was mixed to ensure homogeneity.

The solid materials listed in Table 26 below were premixed andintroduced into the mixer:

TABLE 26 Solid Components Component Parts by Weight ATH - ALCAN,non-treated 1470 Kaneka FM-25 120

The mixture was mixed for 3 minutes at which point the materialtransformed into a paste. A mixture of decorate ATH-filled acrylicparticles (DFAP's) within the size range of 30 to 150 mesh (approx.100-560 microns) was added and mixed in:

Component Parts by Weight DFAP's 630

The mixture was mixed for 20 minutes under a 25″ Hg vacuum (735 mm Hg)during which the material transformed into a thick molding compound ofuniform composition. The molding compound was removed from the mixer andpackaged in bulk form in an airtight plastic bag. The compound wasstored at 5-100C.

An insert was prepared from 0.004″ (0.1 mm) NOMEX® paper (DuPontCompany, Wilmington, Del.) stock with dimensions 9.5″×9.5″. Two chargesof the above formulation, each weighing 195 g, were each prepressed intoa uniform thickness, circular charge about 9″ in diameter. The NOMEX®insert was sandwiched between the charges to create a composite charge.The composite charge was placed into a room temperature 10″×10″ aluminumframe hand mold having a 0.005″ (127 micron) flash gap. The mold wasclosed and placed into a hydraulic press at a platen temperature of 140°C. A pressure of 550 psi (38.7 kg/cm²) was applied immediately. Pressureand heat were maintained for 6 minutes during which the external moldtemperature reached 125° C. for at least two minutes. The mold was thenplaten-cooled under pressure until the external mold temperature reachedabout 80° C. The pressure was then released and the mold was removed andopened. The molded article was removed from the mold to give a sheetapproximately 0.125″ (0.32 cm) thick with a NOMEX® paper encapsulantsuspended in the censor of the article. Adhesion between the encapsulantand the molding compound was excellent.

Example 18 Addition of Acid Functionality to Molding Compound to PromoteAdhesion

A liquid mixture having the components listed in Table 27 below wasprepared. The liquid mixture was introduced into a water-cooled 2.5gallon double planetary mixer (Charles Ross & Son Company; Hauppauge,N.Y.):

TABLE 27 Liquid Mixture Component Parts by Weight Acrylic sirup, 17%V045 solids 762 and 3% Elvacite 2014 solids in MMA Ethylene glycoldimethacrylate 9.8 Lupersol 10M75 2.4 VAZO 67 0.6 Zelec MO 2.5

This liquid mixture was mixed to ensure homogeneity.

The solid materials listed in Table 28 below were introduced insequence:

TABLE 28 Solid Components Component Parts by Weight Calcium Carbonate(Polar Minerals) 1890 Kaneka FM-25 120 Elvacite ® 2041 198

The mixture was mixed for 20 minutes under 25″ Hg vacuum (735 mm Hg) atwhich point the material transformed into a thick molding compound ofuniform composition. The molding compound was removed from the mixer andpackaged in bulk form in an airtight plastic bag. The compound was thenstored at 5-10C.

Example 19 Encapsulation of Aluminum Shoot with Example 18 Composition

An insert was prepared from 0.125″ stock aluminum sheet with dimensions9.625″×9.625″. The sheet was cleaned by sandblasting and isopropanolwash. Just prior to use, the insert was treated with a 1% Zelec® MO inisopropanol solution to enhance adhesion.

Two charges of the Example 18 Composition, each weighing 582 g, wereeach prepressed into a uniform thickness, circular charge about 9″ indiameter. The aluminum sheet insert was sandwiched between the chargesto create a composite charge.

The composite charge was placed into a room temperature 10″×10″ aluminumframe hand mold having a 0.005″ (127 micron) flash gap. The mold wasclosed and placed into a cold hydraulic press and pressed at 150 psi(10.5 kg/cm²) for about 30 seconds to fill the mold. The mold was theninserted into a second hydraulic press with a platen temperature of 140°C. A pressure of 150 psi (10.5 kg/cm²) was initially applied. Pressurewas gradually increased to 550 psi (38.7 kg/cm²) within 3.0 minutes.Pressure and heat were maintained for 7.5 minutes during which time theexternal mold temperature reached 115° C. for at least two minutes. Themold was then platen cooled under pressure until the external moldtemperature reached about 80° C. The pressure was then released and themold was removed and opened. The molded article was removed from themold to give a fully encapsulated aluminum sheet.

Upon evaluation, it was found that the molded article dissipated appliedheat very efficiently: A five minute contact with a hot steel block (inexcess of 220° C.) caused no visible damage while controls without aninternal aluminum core did show irreversible heat damage.

Example 20 One-Sided Application of Example 18 Composition to AluminumSheet

A molding compound having Example 18 Composition, with the exception ofthe use of ALCAN untreated ATH, was prepared using the same procedure.

An aluminum sheet substrate identical to that in Example 16 wasprepared. A single charge of molding compound weighing 420 g wasprepressed into a uniform thickness, circular chase about 9″ indiameter.

The molding compound was placed on the top side of the aluminum sheetand the result composite charge was placed in the mold used in Example19 at room temperature. The mold was closed and inserted into a coldhydraulic press and pressed at about 200 psi (14 kg/cm²) for 30 seconds.The mold was then inserted into a second hydraulic press win a platentemperature of 135° C. A pressure of 150 psi (10.5 kg/cm²) was initiallyapplied. Pressure was gradually increased to 550 psi (38.7 kg/cm²)within 3.0 minutes. Pressure and heat were maintained for 7 minutesduring which time the external mold temperature reached 120° C. for atleast two minutes. The mold was then platen-cooled under pressure untilthe external mold temperature reached about 80° C. The pressure was thenreleased and the mold divas removed and opened. The molded article wasremoved from the mold to give a two layer structure having a singlesided application of filled acrylic material. Upon cooling, the partwarped significantly.

Adhesion of the molded material to the aluminum substrate was found tobe excellent. The interface survived many repeated impacts. Furthermore,when the composite structure was bent, the molded material cracked, butdid not lose adhesion, even upon bending to 90°.

Example 21 One-Sided Application of Molding Compound to Clear AcrylicSheet

A liquid mixture having components listed in Table 29 below wasprepared. The liquid mixture was introduced into a water-cooled 2.5gallon double planetary mixer (Charles Ross & Son Company; Hauppauge,N.Y.):

TABLE 29 Liquid Mixture Component Parts by Weight Acrylic sirup, 24%V045 solids in MMA 726 Ethylene glycol dimethacrylate 11 Lupersol 11 1.5VAZO 67 0.6 Zelec MO 3.1

This liquid mature was mixed to ensure homogeneity.

The following solid materials listed in Table 30 were introduced insequence:

TABLE 30 Solid Components Component Parts by Weight ATH - NLM,silane-treated 1440 Zeeospheres W610 (3M Company, 60 St. Paul, MN)Elvacite ® 2896 120

The mixture was mixed for 3 minutes at which point the materialtransformed into a paste. A mixture of decorative ATH-filled acrylicparticles (DFAP's) within the size range of 30 to 150 mesh was added andmixed in:

Component Parts by Weight DFAP's 690

The mixture was mixed for 30 minutes during which time the materialformed a thick molding compound of uniform composition. The moldingcompound was removed from the mixer and packaged in bulk form in anairtight plastic bag. The compound was stored at 5-10° C.

An insert was prepared from 0.25″ (0.64 cm) thick stock clear acrylicsheet with dimensions 7″×7″. A single charge of the above moldingcompound weighing 425 g was prepressed into a uniform thickness,circular charge about 6″ in diameter. The molding compound was placed onthe top see of the acrylic sheet substrate and the resulting compositecharge was placed in a room temperature, 7″×7″ cavity mold similar tothe mold used mold used in Example 19.

The mold was closed and inserted into a cold hydraulic press and premedat about 200 psi (14 kg/cm²) for 30 seconds. The mold was then insertedinto a second hydraulic press with a platen temperature of 125° C. Apressure of 530 psi (37.4 kg/cm²) was initially applied. Pressure wasgradually increased to 1020 psi (71.9 kg/cm²) within 3.0 minutes.Pressure and heat were maintained for 7 minutes during which theexternal mold temperature reached 120C for at least three minutes. Themold was then platen cooled under pressure until the external moldtemperature reached about 80° C. The pressure was then released and themold was removed and opened. The molded article was removed from themold to give a two layer structure having a single sided application offilled acrylic material. Upon cooler, the part showed a small amount ofwarp.

The resulting molded article was polished to give a very deep aesthetic.Impact testing of the acrylic sheet surface at 6, 12, 18, 36, and 80in-lbs showed little if any damage. Impact testing of the controlmaterials, the clear acrylic sheet or a molded plaque of the moldingcompound, resulted in obvious visual damage at 12 in-lbs andcatastrophic failure at 80 in-lbs.

Example 22 Encapsulation of Corian® Solid Surface Material by Example 8Composition

Corian® solid surface material, 0.25″ (0.64 cm) thickness, was shatteredby hammer impact. Shards of material ranging from 0.5″ to 3.0″ indimension were pieced in the heated mold described in Example 8. A 400 gcharge of the molding compound described in Example 8 was coldprecompressed into a 8.0″ diameter aisle. The charge was then placed inthe heated mold, on top of the broken Corian®. The mold was closed andthe molding cycle described in Example 8 was followed.

The resulting molded article was sanded to expose an interesting patternin which the molding compound encapsulated the broken Corian® pieces toproduce a continuous material.

Example 23 Use of complex pressure profile in molding three dimensionalarticle

A liquid mixture was prepared composed of the following which wasintroduced into a water-cooled 2.5 gallon double planetary mixer(Charles Ross & Son Company; Hauppauge, N.Y.):

Acrylic situp, 24% PMMA 726 (part. polym. MMA) Ethylene glycoldimethacrylate 11.04 Lupersol 11 1.5 VAZO 67 0.6 Zelec MO 3.2

This liquid mixture was mixed to ensure homogeneity.

The following solid materials were then introduced into the mixer:

ATH - ALCAN, non-treated 1473 Caneka FM-20 120 Zinc Stearate 4.5

The mixture was mixed for 2 minutes at which point the materialtransformed into a paste. A mixture of decorative ATH-filled acrylicparticles (DFAP's) within the size range of 2 to 150 mesh (approx. 100microns-10.3 mm) was added and mixed in:

DFAP's 660

The mixture was reed for 15 minutes under 25″ Hg vacuum (735 mm Hg)during which the material transformed into a thick molding compound ofuniform composition. The molding compound was removed from the mixer andpackaged in bulk form in an airtight plastic bag. The compound wasstored at 5-10C.

The above molding compound was evaluated in a nickel-coated aluminum,platen-heated mold which molds a 6 inch (15.2 cm) diameter flowerpotshape having a 4.5 inch (11.4 cm) depth. A toriod-shaped charge weighing753 g was placed in the mold at a mold temperature of 22° C. The moldwas placed in a hydraulic press with platens heated at 185° C., and aninitial pressure of 340 psi (24 kg/cm²) was applied. After 4 minutes,the external mold temperature had reached 100° C. and the pressure wasincreased to 1480 psi (103 kg/cm²). After 6.5 minutes, the pressure wasreduced to 530 psi (37.3 kg/cm²). At 10 minutes, the external moldtemperature had reached 128° C. and the cooling cycle was begun and thepressure was reduced and maintained at 355 psi (25 kg/cm²) untildemolding at 75° C.

The resulting molded article exhibited excellent reproduction of themold cavity dimensions without pressure whitening defects on the areaswhich were perpendicular to the applied force during the molding cycle.

Of course, it should be understood that a wide range of changes andmodifications can be made to the preferred embodiment described above.It therefore is intended that the foregoing detailed description beregarded as illustrative rather than limiting and that it be understoodthat it is the following claims, including all equivalents, which areintended to define the scope of this invention.

What is claimed is:
 1. A composition comprising: (a) from about 10 toabout 25% by weight of a liquid polymerizable material including atleast one volatile monomer reactive material; (b) at least one viscositybuilder; (c) at least one primary thermal initiator having a primarythermal initiator ten-hour half-life temperature; and (d) at least onesecondary thermal initiator having a secondary thermal initiatorten-hour half-life temperature at least about 5° C. greater than theprimary thermal initiator ten-hour half-life temperature; wherein atleast about 0.05% by weight is one or more crosslinking agents.
 2. Thecomposition of claim 1 wherein the secondary initiator ten-hourhalf-life temperature is in the range of from about 60° to about 120° C.3. The composition of claim 1 wherein the composition is at least 95%cured when heated in a closed mold at a temperature of about 100° toabout 145° C. for about 10 minutes or less.
 4. The composition of claim1 wherein the polymerizable material is selected from the groupconsisting of esters of acrylic acid, esters of methacrylic acid,urethane acrylates, urethane methacrylates, epoxy acrylates, epoxymethacrylates, acrylate functionalized unsaturated polyesters,methacrylate functionalized unsaturated polyesters, vinyl monomers,urethanes, epoxies, unsaturated polyesters, siloxanes, silanes, andcombinations thereof.
 5. The composition of claim 4 wherein thepolymerizable material is an ester of acrylic or methacrylic acid withan alcohol having 1-20 carbon atoms.
 6. The composition of claim 1wherein the volatile monomer is selected from the group consisting ofmethyl(meth)acrylate, ethyl(meth)acrylate, acrylonitrile,methylacrylonitrile, vinyl acetate and combinations thereof.
 7. Thecomposition of claim 1 wherein the viscosity builder comprises fromabout 0.1 to about 25% by weight.
 8. The composition of claim 1 whereinthe viscosity builder is a polymeric setting agent having a weightaverage molecular weight greater than about 500,000.
 9. The compositionof claim 8 wherein the setting agent has a Tg equal to or greater thanabout 50° C.
 10. The composition of claim 8 wherein the setting agenthas a weight average molecular weight greater than about 1,000,000. 11.The composition of claim 8 wherein the setting agent has a medianparticle size in the range of from about 2 to about 150 microns.
 12. Thecomposition of claim 11 wherein the setting agent has a median particlesize in the range of from about 30 to about 150 microns.
 13. Thecomposition of claim 8 wherein the setting agent is selected from thegroup consisting of homopolymers and copolymers of acrylic acid,methacrylic acid, esters of acrylic acid, esters of methacrylic acid,vinyl ethers, vinyl esters, acrylonitrile, methacrylonitrile, acrylamid,methacrylamid, styrene, substituted styrene, butadiene, and combinationsthereof.
 14. The composition of claim 1 wherein the primary thermalinitiator comprises from about 0.01 to about 5% by weight.
 15. Thecomposition of claim 1 wherein the primary initiator ten-hour half-lifetemperature is in the range of from about 40f to about 80° C.
 16. Thecomposition of claim 1 wherein the secondary thermal initiator comprisesfrom about 0.001 to about 1% by weight.
 17. The composition of claim 1which further comprises from about 1% to about 20% by weight of anon-crosslinked resin polymer.
 18. The composition of claim 17 whereinthe non-crosslinked polymer resin has a weight average molecular weightof from about 30,000 to about 200,000.
 19. The composition of claim 17wherein the non-crosslinked resin polymer is selected from the groupconsisting of non-reactive materials and reactive materials.
 20. Thecomposition of claim 17 wherein the non-crosslinked polymer is selectedfrom the group consisting of homopolymers of acrylate esters, copolymersof acrylate esters, homopolymers of methacrylate esters, copolymers ofmethacrylate esters, and combinations thereof.
 21. The composition ofclaim 1 which further comprises from about 1% to about 80% by weight ofa filler.
 22. The composition of claim 21 wherein the filler is amineral filler selected from the group consisting of alumina trihydrate,alumina monohydrate, Bayer hydrate, silica, glass spheres, magnesiumhydroxide, calcium carbonate, barium sulfate, ceramic particles, andcombinations thereof.
 23. The composition of claim 21 wherein the filleris a decorative filler selected from the group consisting of polymerparticles, mineral filled polymer particles, pigments, dyes, reflectiveflakes, metal particles, rocks, colored glass, colored sand, woodproducts, and combinations thereof.
 24. The composition of claim 21wherein the filler is a functional filler selected from the groupconsisting of flame retardants, antibacterial agents, and combinationsthereof.
 25. The composition of claim 1 which further comprises fromabout 0.05% to about 3% by weight of a fiber.
 26. The composition ofclaim 25 wherein the fiber is selected from the group consisting ofpolyester, glass, polyaramid, and combinations thereof.
 27. A moldedarticle made from a molding composition comprising (a) from about 10 toabout 25% by weight of a liquid polymerizable material including atleast one volatile monomer reactive material, (b) at least one primarythermal initiator having a primary thermal initiator ten-hour half-lifetemperature, (c) at least one secondary thermal initiator having asecondary thermal initiator ten-hour half-life temperature of at leastabout 5° C. greater than the primary thermal initiator ten-hourhalf-life temperature, wherein at least about 0.05% by weight is one ormore crosslinking agents.
 28. The molded article of claim 27 wherein thearticle comprises a functional core completely encapsulated by themolding composition.
 29. The molded article of claim 27, wherein thearticle is made from at least a firs t charge unit and a second chargeunit, the first charge unit having a molding composition that isdifferent from a second charge unit molding composition.